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Research
Nine studies reviewed by the WWC investigated the effects of Wilson Reading System®. One study (Torgesen et al., 2006) was a randomized controlled trial that met WWC evidence standards. The remaining studies did not meet evidence screens.
Torgesen et al. (2006) examined the effects of Wilson Reading System® on 71 third-grade students in eight school units5 in Pennsylvania. Students in the comparison group participated in the regular reading program at their schools. 6
Extent of evidence
The WWC categorizes the extent of evidence in each domain as small or medium to large (see the What Works Clearinghouse Extent of Evidence Categorization Scheme). The extent of evidence takes into account the number of studies and the total sample size across the studies that met WWC evidence standards with or without reservations. 7
The WWC considers the extent of evidence for Wilson Reading System® to be small for alphabetics, fluency, and comprehension. No studies that met WWC evidence standards with or without reservations addressed general reading achievement.
6 For the purposes of this study, only word-level skill components of Wilson Reading System® were implemented, but the study noted that the complete version contains instructional routines and materials that also focus on comprehension and vocabulary.
7 The Extent of Evidence Categorization was developed to tell readers how much evidence was used to determine the intervention rating, focusing on the number and size of studies. Additional factors associated with a related concept, external validity, such as the students' demographics and the types of settings in which studies took place, are not taken into account for the categorization.
