Found effects

The WWC found Success for All^® to have positive effects in the alphabetics domain, potentially positive effects on general reading achievement, and mixed effects on comprehension

Improvement index

The WWC computes an improvement index for each individual finding. In addition, within each outcome domain, the WWC computes an average improvement index for each study and an average improvement index across studies (see Technical Details of WWC-Conducted Computations). The improvement index represents the difference between the percentile rank of the average student in the intervention condition versus the percentile rank of the average student in the comparison condition. Unlike the rating of effectiveness, the improvement index is entirely based on the size of the effect, regardless of the statistical significance of the effect, the study design, or the analysis. The improvement index can take on values between –50 and +50, with positive numbers denoting favorable results for the intervention group.

The average improvement index for alphabetics is +13 percentile points across the seven studies, with a range of 0 to +32 percentile points across findings. The average improvement index for comprehension is +8 percentile points across the six studies, with a range of 0 to +17 percentile points across findings. The average improvement index for general reading is +10 percentile points across the six studies, with a range of +2 to +19 percentile points across findings.

Summary

The WWC reviewed 110 studies on Success for All^®. One of these studies meets WWC evidence standards; six studies meet WWC evidence standards with reservations; the remaining 103 studies do not meet either WWC evidence standards or eligibility screens. Based on the seven studies, the WWC found positive effects in the alphabetics domain, potentially positive effects in the general reading achievement domain, and mixed effects in the comprehension domain. The conclusions presented in this report may change as new research emerges.