This study examined the effects of different types of cooperative learning environments on low, average, and high ability students' perceptions of the middle school science classroom environment. Subjects were 15 teachers and 1,185 students from the sixth-, seventh-, and eighth-grades of two middle schools. Data were gathered from a variety of sources: (1) a student pretest and posttest using the My Class Inventory measure; (2) classroom teacher reports; (3) informal interviews with teachers; and (4) classroom observations. Students in the no cooperative learning environments perceived the science classroom as more cohesive than students in the average and high cooperative learning environments. Students in the average cooperative learning classes perceived themselves as less competitive than those in the no and high cooperative learning classes. No significant interaction effects were found between the type of cooperative learning environment and ability level. The results suggest that the quality of cooperative learning is a major determiner in how students perceive the science classroom. (A copy of the cooperative learning assessment instrument completed by teachers is provided. Contains 86 references.) (MDM)