Core reading instruction and interventions have differential effects based on student characteristics such as cognitive ability and pre-intervention skill level. Evidence for differential effect based on affective characteristics is scant and ambiguous; however, students with problem behavior are more often non-responsive to core reading instruction and intensive reading interventions. In this study, we estimated the range of students' behavior ratings in which a core reading instruction intervention was effective using a data set including 3,024 students in K-3. Data came from seven independent studies evaluating the Individualized Student Instruction (ISI) Tier 1 reading intervention and were pooled using integrative data analysis. We estimated Johnson-Neyman intervals of student behavior ratings that showed a treatment effect both at the within and between classroom level. ISI was effective in improving reading scores (b = 0.51, p = 0.020, d = 0.08). However, students with very low or very high behavior ratings did not benefit from the approaches (range of behavior rating factor scores: -0.95-2.87). At the classroom level, students in classrooms with a higher average of problem behaviors did not benefit from ISI (average classroom behavior rating factor score: 0.05-4.25). Results suggest differentiating instruction alone is not enough for students with behavior problems to grow in reading ability.