Decodable and levelled reading books - a systematic review

Major policy decisions about the most effective ways to teach reading are informed by research which is ambiguous at best, spurious at worst, based on small scale studies and informed by marketing spin, according to our systematic review on the effectiveness of decodable and levelled readers on enhancing reading outcomes.

In March 2022, with colleagues in the School of Education, we published a systematic review on the quality of the research evidence supporting decodable and levelled reading books. We found that the different styles of phonics readers are not well understood and our latest research shows that the current evidence base supporting both decodable and levelled readers falls short of what’s required to make informed decisions about literacy teaching.

Of the 1865 published articles about decodable and levelled readers, only 19 were deemed appropriate for our review. We found that most studies were small-scale, designed with high risk of bias, correlational or quasi-experimental, or measured non standardised outcomes.

Even when interventions attempted to focus exclusively on exposure to either ‘decodable’ or ‘levelled’ texts, the studies were muddied by mixed approaches and variability in texts. Books labelled decodable or levelled contained elements of both, suggesting the significant role marketing plays in this valuable commercial field.

On average, studies produced small effect sizes with just a trivial difference between decodable and levelled texts.

Our research highlights the need for Government investment in larger scale, higher quality research. While phonics is an integral part of reading instruction, one-size-fits-all policies must be replaced by a diagnostic approach to delivering the right strategy to the right students at the right time.

Our findings call for more, higher quality research on decodable and levelled reading books and support teachers to build their capacity in the teaching of reading, selection of texts and children's love of books.