Low-achieving adolescents are known to have difficulties with reading comprehension. This article discusses how reciprocal teaching can improve low-achieving adolescents' reading comprehension in whole-classroom settings (as opposed to small-group settings) and to what extent intervention effects are dependent on teacher behaviour. Over the course of 1 year, experimental teachers (n = 10) were given extensive training and coaching aimed at using principles of reciprocal teaching, while control teachers (n = 10) used their regular teaching method. Observations of teacher behaviour were focused on instruction of reading strategies, modelling and support of group work and were performed in both experimental and control classes, comprising a total of 369 students (mean age = 13.01). Our study shows that reciprocal teaching contributed to adolescent low achievers' reading comprehension only when experimental teachers provided high-quality strategy instruction. In addition, results suggest that the quality of implementation of reciprocal teaching in whole-classroom settings should receive more research attention.