40 year Meta-Analysis of interventions that support students with or at-risk of dyslexia

Three key take-aways to consider when designing or choosing Tier 3 intervention.

By Robyn Monaghan

As you may have noticed, we love the number '3' at Read3. Mostly, because remembering three things is not too taxing for any of us! And that means no cognitive overload. 

So, here are ‘3 things’ that I learned from a article about interventions that support our Tier 3 students. "Forty Years of Reading Intervention Research for Elementary Students with or at Risk for Dyslexia: A Systematic Review and Meta-Analysis" (Hall et al, 2022) was first published in the International Dyslexia Association’s Reading Research Quarterly in 2022 and reprinted in their recent Special Issue on Dyslexia.  

The article is a review of the last 40 years of research and is uniquely focused on intervention studies of students with or at risk for word reading disabilities (RDs or Dyslexia).

Unlike previous meta-analyses that included studies using both researcher-created and norm-referenced assessment measures, this review only included studies using norm-referenced measures of word reading, spelling, or foundational reading and spelling skills.

The fact that the results of this review did not replicate all the findings of several previous reviews may reflect the stringent standards imposed with regard to research design and methods. After sorting through thousands of intervention studies, the majority of the included studies (77%) were gold-standard randomised control trials (RCTs), and the mean sample size of the studies was above 100. Fifty-three elementary (primary) school intervention studies met the stringent criteria for review, and of those 53 studies, 45 were focused on students in Kinder to Grade 2 (US). 

So let’s get to the ‘3 things’ I took from the review:

Reading interventions focused on specific reading difficulties (RD or Dyslexia) have a significant, positive impact on norm-referenced reading outcomes for all students, but possibly a greater impact on younger students.

The overall effect size (g = 0.33, 95% CI) on normed assessments showed a meaningful improvement for students in Kinder to Year 5. There was no significant difference in outcomes by grade level, although, descriptively speaking, the studies with students in Grades 3-5 were associated with smaller effects (g = 0.16) than studies with students in Grades K-2 (g = 0.36). 

As interventions with an effect size of 0.33 are more likely to close the achievement gap, interventions may be more effective for children in kindergarten than for children in Grade 5. However, more research was recommended for upper elementary students who were under-represented in this review and who are at risk for developing psychosocial and behavioural difficulties. With regards to policy decisions, it may be both wise and cost-effective for schools to intervene early if they are faced with a decision about how to direct limited intervention resources.

The following moderators did not affect intervention outcomes:

  • Multisensory interventions did not improve outcomes (g = 0.20) compared to other methods not characterised as multi-sensory i.e., evidence-based explicit, systematic approaches to foundational skills instruction (g = 0.34)
  • Morphology or vocabulary instruction, encoding instruction, or phonemic awareness instruction in addition to word reading instruction did not make a significant difference to the impact of intervention. Interventions that provided morphology or vocabulary instruction as well as providing word reading instruction (g = 0.34) yielded very similar effects to word reading interventions without either component (g = 0.33). However, the authors noted a slight advantage for phonological awareness instruction and stated that, descriptively speaking, interventions with a PA component outperformed (g = 0.38) those without a PA component (g = 0.22), concluding that “it may be beneficial (or at least may not be less beneficial) to provide PA instruction in addition to instruction in word reading for students with more severe word-reading difficulties”. 
  • One-on-one versus small-group interventions did not affect outcomes.  Descriptively speaking, studies in the present review that provided instruction to small groups of students appeared to have slightly smaller effects (g = 0.20) than studies that provided instruction one-on-one (g = 0.30). However, this difference was not statistically significant. This finding is important for schools considering resource allocation and intervention scalability.

The following moderators did affect intervention outcomes:

  • Dosage is a key factor in intervention outcomes. Higher dosage interventions (100 or more sessions) yielded slightly larger effect sizes on Grade K-3 reading outcomes (g = 0.39). It was suggested that intervention intensity may be particularly important in the context of students who have significant word RDs. 
  • Adding spelling instruction to reading interventions enhanced effectivenessInterventions with spelling instruction in addition to word reading instruction were more effective (g = 0.37) than those without a spelling instruction component (g = 0.23). When selecting foundational reading interventions for students with or at risk for dyslexia, opt for multicomponent interventions that include both word reading and spelling components.


Practice Implications

The findings support the provision of reading interventions focusing on foundational literacy skills to improve reading outcomes for students with or at risk for dyslexia. The study underscored the value of early interventions that are of sufficient intensity (dosage >100 hours) that include spelling instruction and are tailored to the specific needs of students.

The authors suggested that future research is needed that can answer the question: Is it necessary for students with dyslexia to receive instruction that is qualitatively different (e.g., such that it must be provided by different teachers, in different settings, using different materials) than that provided to students with broadly defined RDs?

Now that is a study we would love to see!

On a personal note:

It is very encouraging to see the significance of intervention that is designed specifically for those with reading disorders being flagged. At Read3 we strive to provide the most up-to-date, evidence-based intervention for these children. Reviewing the findings from such a rigorous meta-analysis we feel confident we are on the right track, look forward to being part of the growing movement to support our most at-risk readers.

If you have any comments, please feel free to share them below 👇 or email us.  


Hall, C., Dahl-Leonard, K., Cho, E., Solari, E., Capin, P., Conner, C., Henry, A., Cook, L., Hayes, L., Vargas, I., Richmond, C., & Kehoe, K. (2022). Forty Years of Reading Intervention Research for Elementary Students with or at Risk for Dyslexia: A Systematic Review and Meta‐Analysis. 

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