The aim of this study was to investigate the effects of intervention, combining instruction in cooperative learning and reading comprehension strategies on students’ reading comprehension in grade 5. The teachers in the experiment group implemented the intervention while the teachers in the control group received training in reading comprehension strategies and taught as usual. Students in the experiment group and control group participated in tests of reading comprehension before and after the intervention. The results showed that being a part of the experiment group did not lead to greater gains in reading comprehension above the control group. Students of teachers who did not fully implement the intervention attained higher scores on reading comprehension than students in the control group. Students of teachers who fully implemented the intervention, on the other hand, received lower scores. The results are discussed with regard to research on teachers’ integration of intervention into their instructional routines.