The analysis reviewed 71 studies of reading interventions, each of which had an intervention and control group, post-tests, and follow-up data an average of 11 months later. Among the findings were that normal readers appeared to profit least from reading interventions, particularly at follow-up. Improvement was not sustained for interventions in preschool: effect sizes fell from +0.34 to +0.12 at follow-up. By contrast, in Years 2 and 3, the effect size only diminished from +0.40 to + 0.26, and for Years 4 and 5, the effect size increased from +0.35 to + 0.43 at follow-up.
The greatest effect sizes at follow-up appeared to result from interventions with a comprehension component.
Source: A Meta-Analysis of the Long-Term Effects of Phonemic Awareness, Phonics, Fluency, and Reading Comprehension Interventions (2016), Journal of Learning Disabilities.