Found effects

The WWC found Accelerated Reader to have no discernible effects for reading fluency, mixed effects for comprehension, and potentially positive effects for general reading achievement

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 based entirely on the size of the effect, regardless of the statistical significance of the effect, the study design, or the analyses. The improvement index can take on values between –50 and +50, with positive numbers denoting results favorable to the intervention group.

The improvement index for reading fluency for third grade students is +3 percentile points for one outcome in one study. The average improvement index for comprehension for third grade students is 0 percentile points with a range of –12 to +12 percentile points for one outcome in both studies. The average improvement index for general reading achievement is +16 percentile points with a range of +10 to +25 percentile points across kindergarten, first, and second grade students in one study.

Summary

The WWC reviewed 100 studies of Accelerated Reader or some of its components. Two of these studies meet WWC evidence standards; the remaining studies do not meet WWC evidence screens. Based on these two studies, the WWC found no discernible effects in reading fluency, mixed effects in comprehension, and potentially positive effects in general reading achievement. The evidence presented in this report is limited and may change as new research emerges.