Found effects

The WWC found Direct Instruction to have no discernible effects for oral language, print knowledge, cognition, or math

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 average improvement index for oral language is +1 percentile point for the one study, with a range of -7 to +6 percentile points across findings. The improvement index for print knowledge is -3 percentile points for the one outcome in the study. The average improvement index for cognition is -1 percentile point for the one study, with no range across findings because the improvement index for each of the two measures is also -1. The improvement index for math is +8 percentile points for the one outcome in the study.

Summary

The WWC reviewed six studies on Direct Instruction. One study met WWC evidence standards with reservations. The remaining studies did not meet WWC evidence screens. Based on the study included in the overall rating of effectiveness, the WWC found no discernible effects for oral language, print knowledge, cognition, or math. The evidence presented in this report is limited and may change as new research emerges.