focusing on mathematics and
reading studies reviewed in the U.S. Department of Education's WhatWorks Clearinghouse (WWC), found that measures that
are “inherent” to the treatment (covering content not taught in the control group) are associated with effect sizes that are
much higher compared to measures of the curriculum taught in experimental as well as control groups (d ¼ 0.45 vs.
d ¼ 0.03). By contrast, Schroeder et al. (2007) in their meta-analysis, where 47 out of 62 achievement tests were locally
constructed, found no difference in outcome (d ¼ 0.73 and d ¼ 0.75 resp.).
1.4. Teaching