Abstract: We included 14 studies with 923 participants in this review. Studies took place in Australia, Canada, the UK, and the USA. Six of the 14 included studies were funded by government agencies and one was funded by a university grant. The rest were funded by charitable foundations or trusts. Each study compared phonics training alone, or in conjunction with one other reading-related skill, to either no training (i.e. treatment as usual) or alterative training (e.g. maths). Participants were English-speaking children or adolescents, of low and middle socioeconomic status, whose reading was one year, one grade, or one standard deviation below the level expected for their age or grade for no known reason. Phonics training varied between studies in intensity (up to four hours per week), duration (up to seven months), training group size (individual and small groups), and delivery (human and computer). We measured the effect of phonics training on seven primary outcomes (mixed/regular word reading accuracy, non-word reading accuracy, irregular word reading accuracy, mixed/regular word reading fluency, non-word reading fluency, reading comprehension, and spelling). We judged all studies to be at low risk of bias for most risk criteria, and used the GRADE approach to assess the quality of the evidence. There was low-quality evidence that phonics training may have improved poor readers' accuracy for reading real and novel words that follow the letter-sound rules (standardised mean difference (SMD) 0.51, 95% confidence interval (CI) 0.13 to 0.90; 11 studies, 701 participants), and their accuracy for reading words that did not follow these rules (SMD 0.67, 95% CI 0.26 to 1.07; 10 studies, 682 participants). There was moderate-quality evidence that phonics training probably improved English-speaking poor readers' fluency for reading words that followed the letter-sounds rules (SMD 0.45, 95% CI 0.19 to 0.72; 4 studies, 224 participants), and non-word reading fluency (SMD 0.39, 95% CI 0.10 to 0.68; 3 studies, 188 participants), as well as their accuracy for reading words that did not follow these rules (SMD 0.84, 95% CI 0.30 to 1.39; 4 studies, 294 participants). In addition, there was low-quality evidence that phonics training may have improved poor readers' spelling (SMD 0.47, 95% CI –0.07 to 1.01; 3 studies, 158 participants), but only slightly improve their reading comprehension (SMD 0.28, 95% CI –0.07 to 0.62; 5 studies, 343 participants). Phonics training appears to be effective for improving literacy-related skills, particularly reading fluency of words and non-words, and accuracy of reading irregular words. More studies are needed to improve the precision of outcomes, including word and non-word reading accuracy, reading comprehension, spelling, letter-sound knowledge, and phonological output. More data are also needed to determine if phonics training in English-speaking poor readers is moderated by factors such as training type, intensity, duration, group size, or administrator.

Plain-language summary: The search, updated in May 2018, identified 14 studies that tested phonics training in 923 English-speaking poor readers. The studies took place in Australia, Canada, the UK, and the USA. Six of the 14 included studies were funded by government agencies and one was funded by a university grant. The rest were funded by charitable foundations or trusts. Each study compared phonics training alone, or with one other reading-related skill, to either no training (i.e. treatment as usual) or alterative training (e.g. maths). Participants were English-speaking children or adolescents, of low and middle socioeconomic status, whose reading was one year, one grade, or one standard deviation (distance from the average) below the level expected for their age or grade for no known reason. Phonics training varied between studies in frequency (up to four hours per week), duration (up to seven months), training group size (individual and small groups), and delivery (human and computer). We measured the effect of phonics training on poor readers' ability to read words and novel words (non-words) accurately and fluently, as well as their comprehension of text, and their knowledge of letter-sound rules (letter-sound knowledge) and speech sounds (phonological output). We found that phonics training in English-speaking poor readers probably improved irregular word reading accuracy, mixed/regular word reading fluency, and non-word reading fluency. It may also have improved mixed/regular word reading accuracy, non-word reading accuracy, reading comprehension, spelling, letter-sound knowledge, and phonological output. The overall quality of the evidence ranged from low to moderate. This was primarily due to large differences in the size of phonics-training effects between studies. More studies are needed to improve the precision of the outcomes. The evidence suggests that phonics training can improve literacy in English-speaking poor readers. The positive effects of phonics training on all reading-related outcomes suggests that phonics training is not harmful for poor readers.