This research examined the important factors influencing the mathematics achievement of students in middle schools by hierarchically specifying the personal and contextual variables. The study focused on the effect of school climate at the class level and the effects of student gender, attitude toward mathematics, educational aspiration, parent education level, and language spoken at home at the student level. A multilevel analysis was conducted on United States middle grade student data for 8,912 eighth-grade students from 212 schools who participated in the Trends in International Mathematics and Science Study (TIMSS) 2007. The results revealed that teacher perceived school climate showed a significant relationship with the average student math performance. A cross-level interaction effect for the student's attitude toward mathematics and teacher perceived school climate was also statistically significant. Five predictors at the student-level were found to be significantly related to middle school student mathematics achievement: a student who had a positive attitude toward mathematics, who was male, who spoke English as a primary language, and whose parents were highly educated was likely to display a high level of mathematics performance. Implications of these findings are discussed applying socialization of gendered domain of school subject perspectives. (Contains 2 figures and 3 tables.)