Examining Differential Intervention Effects: Do Individualized Student Intervention Effects Vary by Student Abilities and Characteristics?

The Individualized Student Instruction (ISI) intervention was designed to help teachers increase their use of differentiated core reading instruction, to optimize student growth by providing appropriate amounts of code- and meaning-focused instruction. Based on the results from original studies on ISI, it is still unclear if differentiated instruction can mitigate the influence of individual differences, and if this is similar for all students. Using integrative data analytic techniques, we combined data from six randomized control trials on the ISI intervention conducted in kindergarten and first grade and obtained a dataset with a total sample of 3,144 students in Grades K and 1. We then fit conditional multilevel quantile regression models to examine differential effects on word reading and vocabulary outcomes and the moderating effect of pre-intervention skills. The model coefficients did not indicate a treatment effect of the ISI intervention on either vocabulary or word reading skills. We discuss these results in the light of the importance of data sharing and registered reports to uncover what works for which students under which conditions.