A study examined the factors determining the learning environments of agricultural science classes in Nigeria and the effects of those learning environments on student attitudes and achievement. The study sample, which was selected to be representative of schools from Nigeria's northern and southern regions and urban and rural areas, consisted of 1,175 students in 50 secondary-level agricultural science classes in 20 different schools located in 8 states. The "Constructivist Learning Environment Survey" (CLES) and "Individualized Classroom Environment Questionnaire" (ICEQ) were used to determine student perceptions of classroom environment, the "School-Level Environment Questionnaire" was used to identify teacher perceptions of school-level environment, and the "Test of Enquiry Skills" and "Test of Related Science Attitudes" were used to measure student achievement. Analysis-of-variance, simple correlation, and multiple regression analysis were used to analyze the various data. Higher scores on the negotiation, autonomy, investigation, and differentiation scales of the CLES and ICEQ were associated with more positive student attitudes and higher enquiry skill scores. All five dimensions of school-level environment (affiliation, professional interest, participatory decision making, innovativeness, and resource adequacy) had a significant effect on classroom-level negotiation, autonomy, and investigation. (Contains 26 references.) (MN)