Spelling is the ability to recognise and reproduce spoken language in a correct sequence of written symbols (Moats 2010; Mpiti 2012; Santoro, Coyne & Simmons 2006; Weiser & Mathes 2011). While there is not consensus on the development of spelling across languages, the main theories and perspectives are briefly reviewed below. These theories are, however, based mainly on English studies. Cross-linguistic studies on spelling development are relatively limited (Babayiǧit 2009).

The earliest and most well-known model of spelling development was introduced by Gentry (1982), who suggested that learning to spell takes place in five stages, from reliance on phonological knowledge to a dependence on orthographic and morphological knowledge (Bourassa & Treiman 2010; Schlagel 2007). He posited that learners begin at the ‘precommunicative stage’ when the learner has partial knowledge of the alphabet but does not yet understand letter-sound relationships (Gentry 1982). At this stage, spellings are characterised by the strategy of randomly selecting letter strings to represent words (Ellis 1994). The second stage is the ‘semi-phonetic stage’, when learners have some grasp of letter– sound relationships, with spellings containing a partial mapping of phonetic content. It is at this stage that children often represent words, sounds or syllables with letters that match their letter names, for example, ‘U’ for ‘you’ (Ellis 1994). In the ‘phonic’ or third stage, they begin to use phonics to map letter-sound correspondences, for example, ‘haws’ for ‘house’ (Ellis 1994). In the later stages (transitional and correct stages), learners move from phonological spelling and start to incorporate morphological and orthographic knowledge when spelling (Gentry 1982).

Critiques of the stage theory have stated that it provides a linear account of spelling and oversimplifies the picture with little consideration of the linguistic characteristics of the language being learnt (Bourassa & Treiman 2010). For example, different languages have specific morphological and orthographic knowledge needed to be acquired by learners and therefore some skills are grasped more easily than others and at different periods in spelling development (Bourassa & Treiman 2010). Nevertheless, the theory acknowledges the developmental shifts when learning to spell, especially from a reliance on phonological knowledge to a dependence on orthographic and morphological knowledge (Bourassa & Treiman 2010; Ravid 2012; Schlagal 1989). However, Babayiǧit (2009) argued that children may utilise both phonological and orthographic spelling processes in the early stages of development depending on the demand of the task, their level of alphabetic knowledge, phonological awareness and print experience.

Cross-linguistic studies which have examined spelling development and the specific skills most relevant for spelling development across languages are growing in number but most studies have focused on English (Caravolas 2004; Georgiou et al. 2020). Nevertheless, there is a general acknowledgment that spelling relies on letter-sound knowledge (e.g. Finnish, Greek and English: Georgiou et al. 2012), phonological awareness (e.g. English, Spanish, Slovak, and Czech: Caravolas et al. 2012), morphological awareness (e.g. English: Apel et al. 2012), orthographic knowledge (e.g. English: Apel 2009) and reading experience (e.g. Finnish: Leppänen et al. 2006; Lerkkanen et al. 2004; French, Dutch, German and Greek; Georgiou et al. 2020). As noted above, phonological awareness and reading are related to spelling ability. The interrelation between these concepts are addressed in more detail in the next sections.

Phonological awareness is defined as the awareness of the sound structure of a language and the ability to perceive or manipulate sounds in a linguistic sequence (Moll et al. 2014). Phonological awareness is typically divided into the following linguistic components: onset-rime, syllables and phonemes (Anthony & Francis 2005; Chard & Dickson 1999; Stahl & Murray 1994; Treiman 1991).

There is an extensive body of research which confirms that phonological awareness is a significant predictor of both reading and spelling across different languages (Adams 1990; Babayiğit & Stainthorp 2007; Bryant et al. 1990; Caravolas, Volín & Hulme 2005; Hulme & Snowling 2015; Landerl & Wimmer 2008; Zarić et al. 2020). Notably it has been revealed that phonemic awareness is the strongest predictor of early word reading in alphabetic languages (Melby-Lervåg, Lyster & Hulme 2012). Similarly, research on the Southern-Bantu languages converge on the importance of phonological awareness for reading (Lekgoko & Winskel 2008; Malda, Nel & Van De Vijver 2014; Wilsenach 2013, 2015, 2019). However, the relationship between spelling and phonological awareness in the Southern-Bantu languages is less clear.

International research reports that phonological awareness plays a concurrent and longitudinal role in spelling performance (Caravolas et al. 2012; Harrison et al. 2016; Landerl & Wimmer 2008; Lervåg & Hulme 2010; Veber Nielsen & Juul 2016). In particular, research has suggested that phonological awareness and spelling should have a stronger relationship in languages with transparent orthographies due to the consistent nature of the phoneme to grapheme and grapheme to phoneme mappings (e.g. Leppänen et al. 2006; Öney & Durgunoglu 1997). Phonological awareness is a necessary prerequisite for the conversion of phonemes to graphemes, the primary requirement of spelling across all alphabetically written languages. However, as noted in Georgiou et al. (2012), these assertions are not made in consideration of the individual characteristics of languages with transparent orthographies.

De Bree and Van den Boer’s (2019) study of Dutch spelling in grades 1 and 2 found that phonological awareness significantly predicted spelling in regression analyses. However, when reading was added into their regression model, phonological awareness along with other contributors (visual attention span and rapid automatised naming) were no longer significant, confirming the importance of reading for early spelling (De Bree & Van den Boer 2019; Desimoni, Scalisi & Orsolini 2012; Keuning & Verhoeven 2008; Leppänen et al. 2006) and reaffirming the link between phonological awareness and reading (De Bree & Van den Boer 2019; Frith 1985). De Bree and van den Boer (2019) suggest that phonological awareness constitutes mainly as an underlying skill of reading and that phonological awareness relates to spelling but that it is not necessarily sufficient in explaining how learners convert phonemes to graphemes. Thus, they suggest that further research is needed to investigate specific correlates and underlying skills related to spelling, for example, vocabulary knowledge, morphological awareness, and orthographic learning (De Bree & Van den Boer 2019; Kim, Apel & Al Otaiba 2013). These results are of particular significance as Dutch, like isiXhosa, is considered to have a transparent orthography in which the regularity of the orthographic system is higher in grapheme–phoneme relations (forward regularity, e.g. reading,) than it is in phoneme–grapheme relations (backward regularity, e.g. encoding) (Bosman, Vonk & Van Zwam 2006; Daries & Probert 2020). For example, in isiXhosa, there are a number of complex graphemes for which multiple letters represent single sounds e.g. <dl>, <ph>, <tsh> (Spaull et al. 2020).

Southern African research on spelling in languages other than English confirms the relationship between phonological awareness and spelling. Phonological awareness was associated with spelling ability in Herero for a sample of grade 2 to grade 5 learners (Veii 2003), in Oshikwanyama for a sample of grade 1 learners, assessed again in grade 2 (Nghikembua 2020), and in isiXhosa for a small sample of grade 3 isiXhosa learners (Diemer 2015). Makaure (2021) found similar results with 134 Northern Sotho-English bilingual learners. The study’s findings showed that phonological skill was one of the best predictors of Northern Sotho spelling. Common to all these studies was the need to develop tests of phonological awareness suitable to each language, and sample. These were real word phonological awareness tests of phoneme isolation using sound matching (e.g. Which one is the odd one out: sava, sina, zuva? (Veii 2003)), real-word phoneme isolation tasks (e.g. What is the first sound of pedu? [Nghikembua 2020]), and pseudoword tasks of segmenting (e.g. Break up this word into its sounds: gofotsa) and elision (Say hlenama without /hl/ [Diemer 2015]). Although various tasks have been used, an effect of phonological awareness on spelling was found across different South African languages and grade levels.

Reading can be understood as the starting point of spelling, as what learners are able to read can provide the basis for what they are able to spell (Bear et al. 2004). When learners read or practise reading, they are recognising common letter patterns in words, mapping sounds onto letters and letter patterns which develops their orthographic representations of words necessary for spelling (Conrad 2008). This suggests that spelling can provide an indication of learners’ reading ability. Furthermore, Gentry (2004:11) states that ‘learners learn to read by spelling’ and knowledge of the alphabetic principle necessary for spelling supports reading. This is because spelling and reading rely on the same lexical representations (Ehri 1997, 2005; Perfetti 1997; Templeton 2004).

While the exact nature of the relationship between reading and spelling is not clearly defined and understood, there are a number of studies which indicate strong and significant correlations between spelling and reading ability (Abbott et al. 2010; Caravolas, Hulme & Snowling 2001; De Bree & Van den Boer 2019; Ehri 1997; Foorman et al. 1991; Georgiou et al. 2020; Ritchey 2008). Whilst there are few studies which examine the effect of reading on spelling in the African languages found in Southern Africa, existing studies confirm that reading ability is associated with spelling. For example, Nghikembua (2020) reported a significant association between grade 1 reading and grade 2 spelling using a path analysis model in Oshikwanyama. Given cross-linguistic evidence on the role of reading for spelling in orthographies which vary in transparency (e.g. Georgiou et al. 2020), one might expect to find a positive association between reading ability and spelling in other African languages.

Study 1 was exploratory. We used cross-sectional data first reported by Daries and Probert (2020).

The descriptive statistics and correlations among the variables are presented in Table 1. Visualisations of the spread of the raw data, and assumptions of the linear regression, are presented in the OSF project https://osf.io/cesgf/. Phonological awareness and reading had moderate to strong correlations with spelling (r above 0.65). Age was weakly correlated with spelling and reading, and had a weak negative correlation with phonological awareness (r = -0.35, p = 0.04). We categorised the sample into reading fluency groups using the suggested isiXhosa fluency benchmarks for children in grade 3 (Ardington et al. 2021, see Table A1 in the appendix). In our sample, 31 children (61%) were not reading at the lower fluency threshold of 20 WCPM. 17 children (33%) read within the fluency zone of 20–34 WCPM which was a similar proportion found for isiXhosa learners in term 1 of grade 3 (Ardington et al. 2021). Only one child read above the upper threshold of 35 or more WCPM. The sample includes slower readers than those sampled by Ardington et al. (2021).

The results of the multiple linear regression and quantile regression are presented in Table 2, following, and in Figure 1 in the next section. The results were different for each estimation method. At the mean, both reading and phonological awareness were significant predictors accounting for 39.4% and 14.7% of the variance, respectively (see Linear Regression in Table 2). The confidence intervals for reading and phonological awareness overlapped one another, indicating that the slopes may not be different from one another. The trend in the quantile regression results was that the difference in ability on spelling was larger for a participant 1 SD higher on reading (slope = 2.36), than phonological awareness (slope = 1.33) at the 10th quantile, and the trend was reversed at the 50th quantile (reading slope = 0.74, phonological awareness slope = 2.07). However, there was no difference in performance for participants at the mean or 1 SD above the mean on the predictors at the 90th quantile, possibly because the participants at the 90th quantile were perfoming at ceiling level on the spelling task. A quantile comparison test indicated that the slopes did not differ across quantiles, which is confirmed also by the overlap in confidence intervals at each quantile.

Our first study was exploratory, and examined to what extent phonological awareness and reading predicted spelling at the mean, and at different quantiles of spelling performance, corresponding to low, medium and high performance on spelling. With reference to the first research question, we found that at the mean (linear regression), both reading and phonological awareness were significant (unique) predictors of spelling. With reference to the second research question, the quantile regression presented evidence that the strength of the predictors may differ at different levels of spelling ability, with reading ability leading to larger differences in spelling at the 10th quantile, and phonological awareness ability leading to larger differences in spelling ability at the 50th quantile. At the 90th quantile, the participants were at ceiling levels of performance in spelling. However, given the small sample size, all confidence intervals were wide, leading to the slope differences not reaching significance.

Study 1 provided evidence that both phonological awareness and reading are significant predictors of real word spelling in this sample, but there was insufficient precision to address whether these relationships do differ by levels of spelling ability.

We used secondary data from a collaborative literacy intervention project to perform a conceptual replication of study 1. The intervention project focuses on strengthening the isiXhosa literacy skills of children in grades 1 to 3 in five schools in low socioeconomic areas in the Eastern Cape of South Africa, as well as the upskilling and capacity building of teachers and literacy ambassadors (classroom assistants). Study 2 draws participants from the same population of grade 3 learners in low-income Quintile 3 township schools in the Eastern Cape. All participants attended schools in which the intervention took place i.e. there was no comparison/control group. The intervention results are not of interest to this article and will not be considered further.

Study 2 differs notably from study 1 in the following ways: phonological awareness was measured using a shorter task, the data was from an intervention project, participants were assessed at the start and end of grade 3, and the participants were sampled in 2021 which is the second year that COVID-19 impacted the quantity and quality of education in South Africa.

Ethical clearance was obtained from the Rhodes University Ethical Standards Committee for both study 1 (RU-HSD--2019-0461-452) and study 2 (RU-HSD- 2020-1195-3307). Ethical clearance was obtained from the Eastern Cape Department of Basic Education for each study.

The descriptive statistics and correlations among the variables are presented in Table 3. Visualisations of the spread of the raw data, and assumptions of the linear regression, are presented in the OSF project https://osf.io/cesgf/. On average, the oral reading fluency of the group was low at the start of grade 3 (M = 12.7, SD = 13.6), and had improved by the end of grade 3 (M = 30.7, SD = 19). There was a large-effect size difference in the reading abilities of study 2 participants at the end of grade 3 compared to study 1, t(247) = -5.29, p < 0.001, d = -0.84, 95% CI [-1.16, -0.52]. There were more learners at or above the threshold of 20 WCPM in study 2 (70%) than in study 1 (37%) at the same point in the academic year. There was no difference for spelling between the studies at the same point in the academic year, t(247) = 0.94, p = 0.348, d = 0.15, 95% CI [-0.16, 0.46]. The phonological awareness scores could not be compared directly because of the different way the construct was measured in each study. The correlations among variables was moderate to strong, which was similar to study 1. The correlation between phonological awareness, and reading and spelling was slightly lower than in study 1, probably due to the lower reliability of the phonological awareness task in study 2. As in study 1, age was negatively and weakly correlated with phonological awareness at the end of grade 3. Additionally, the same negative correlation was found for spelling at the end of grade 3 in study 2.

The results of the linear mixed model and linear quantile models are presented in Table 4 and Figure 1. First, the intra class correlation (ICC) was examined to determine whether school or teacher random effects should be included in the model. The ICC for school level was 0.161 at the start of grade 3 and 0.025 at the end of grade 3, and at teacher level the ICC was 0.084 at the start of grade 3 and 0.032 at the end of grade 3. We decided to use school random effects at the start of grade 3 and teacher random effects at the end of grade 3 because these levels affected the spelling outcome the most. We then fitted maximal models with varying intercepts, varying intercepts and slopes (uncorrelated) and varying intercepts and slopes (correlated). Only the varying intercepts models converged and were used for further analysis. In the final step, we determined the fixed effects by comparing a null model (only the cluster predictor) to successive models adding age, then reading, then phonological awareness. For both timepoints, the model fit improved with the addition of each fixed effect. Thus, we report the models using varying intercepts for school (start of grade 3) and teacher (end of grade 3) with all three predictors, in Table 4.

The linear mixed model, which estimated the mean, found that at both the start and end of grade 3, reading and phonological awareness were significant predictors of spelling. The 95% CI for reading at the end of grade 3 (beta = 1.47, [0.9, 2.0]) overlapped with the estimate in study 1 (beta = 1.27, [0.57, 2.14]. The 95% CI for phonological awareness for study 2 (beta = 1.71, [1.2, 2.2]) and study 1 (beta = 2.11, [1.32, 3.14] also overlapped, despite the change in measurement. As expected, the width of the 95% CI was smaller in study 2 because of the larger sample. The 95% CIs of the start of grade 3 estimates (reading beta = 2.97, [2.5, 3.5], phonological awareness beta = 0.76, [0.4, 1.2]) did not overlap with those at the end of grade 3 for either study 1 or 2; the reading estimate was much larger, and the phonological awareness estimate much smaller.

The linear mixed quantile regression results indicated that participants who had 1 SD higher ability in reading and phonological awareness had a similar increment in spelling score compared to participants at mean of these variables at the 10th and 50th quantiles at the end of grade 3 (Table 4). At the 90th quantile, neither were significant, replicating what was found in study 1. The clustering at teacher level accounted for a large proportion of the variance at the 90th quantile (ICC = 0.294) compared to the other quantiles (ICC = 0.016_10th, ICC_50th = 0.023). The start of grade 3 results established reading as a significant predictor at all three tested quantiles. Participants with 1 SD higher on reading had higher scores on spelling than those at the mean at each quantile, with a slightly smaller difference at the 10th quantile. Participants who differed by 1 SD on phonological awareness only had higher scores on spelling at the 50th quantile. The school that a participant was in had the largest effect at the 10th quantile (ICC = 0.093), than the other two quantiles (ICC_50th = 0.008, ICC_90th = 0.014).

In the second study, we aimed to replicate the findings of study 1. We found evidence in support of our first hypothesis that reading and phonological awareness are related to spelling ability. These findings were replicated at the mean of spelling where the 95% CIs of the estimates overlapped for study 1 and study 2. We also find evidence in support of our second hypothesis. Comparing the start and end of grade 3 linear mixed model results in study 2, we found that reading was a stronger predictor of spelling at the lower ability level (i.e. start of grade 3) than at the higher spelling ability level (i.e. end of grade 3). The mixed-quantile regression results partially supported H(1)2a and H(1)2c. At the lower end of spelling ability, 1 SD change in reading lead to larger gains in spelling compared to 1 SD change in phonological awareness. When spelling ability was at ceiling level, neither phonological awareness nor reading were significant predictors. We had hypothesised that phonological awareness would become a stronger predictor of spelling at the mid-range of spelling ability. Although it did reach significance at the 50th quantile at the start of grade 3, and the 10th and 50th quantiles for the end of grade 3, a 1 SD change in phonological awareness compared to someone at the mean lead to an increase in spelling scores that was lower than those of similar magnitude to a 1 SD difference on reading.