Words of warning: "Well-designed experiments yielding positive outcomes provide the strongest evidence that PA caused the improvement in reading. Although all of the studies in our database consisted of experiments, some were better designed than others. Studies varied in whether they used treated or untreated control groups. The use of untreated controls receiving no special attention from researchers runs the risk of Hawthorne effects as an explanation for differences favoring the treatment group. Studies varied in whether students were randomly assigned to treatment and control groups, or whether a quasi-experimental design was used in which existing groups were assigned to conditions, or whether students were matched and assigned to conditions. Although random assignment is preferable, researchers may be limited to a quasi-experimental design when classrooms in schools are studied. We examined whether positive effects of PA instruction emerged primarily from the weaker designs or whether effects were strongest in the best designed experiments.”
Quotes with potential (B&vI refers to Bus and van Ijzendoorn, 1999)
"B&vI (1999) obtained only partial support for this. They found that individualized instruction was less effective than small-group instruction for teaching PA, but was more effective for promoting transfer to reading. Replication of this effect with our larger database was considered important."