Many low-achieving adolescents struggle with reading comprehension. Since it is a fundamental skill in many school subjects, poor reading comprehension has serious implications for students’ educational success and, consequently, for their later societal careers. Since the 1980’s, reading programs have focused on teaching reading strategies in order to foster reading comprehension. However, results of research in teaching reading strategies to low-achieving students are mixed. The general aim of this dissertation is to gain further insight into the effects of instructing reading strategies on reading comprehension to students in whole-classroom settings. It does so, on the one hand by an experimental study of a specific reading strategy intervention, and on the other hand by a meta-analysis of 52 published studies reporting on reading strategy interventions conducted in whole-classroom contexts.