Across two years, we examined the effects of teachers' attempts to implement computer supported collaborative learning (CSCL) communities in classrooms in two high schools on students' knowledge building, strategic learning, and perceptions of the classroom environment. In year one, 429 (fall) and 317 (spring) students in the classes of 8 teachers and in year two, 946 students in the classes of 18 teachers participated. Students in classes where CSCL communities were more fully established reported more knowledge building goals and activities, more question asking, and higher perception of collaboration with fellow students. Students' reports of knowledge building, strategic learning, and perceptions of the classroom were also associated with their classroom achievement. Results suggest that implementing practices and technology supportive of CSCL communities can foster increased student knowledge building and enhance students' perceptions of collaboration in regular classroom environments.