Students' behavior and emotional well being are instrumental for their success in the school setting. The present study examined the effects of behavioral problems on the academic performance of students three years later. The behavioral problems consisted of individual externalizing, internalizing, and inattentive behaviors. Next, this study examined the classroom-level of externalizing behaviors and the cross-level interaction between individual-level behavioral problems and classroom-level externalizing behaviors on the academic performance of students. Further, the moderating effects of sex and FARM on the associations between behavioral problems and academic performance were studied. The academic performance of students was measured by teacher reported grades and standardized achievement assessment scores. The participants were fifth grade students (N = 2,677) in 193 classrooms from 45 public schools in the mid-Atlantic region. Results indicated that individual inattentive behaviors and classroom-level of externalizing behaviors negatively and significantly predicted academic performance three years later. Although it was hypothesized that the negative effects of behavioral problems on the academic performance of students would be greater being in classrooms with higher average levels of externalizing behaviors, the opposite was found. The negative effects of behavioral problems on academic performance were greater for students who were in classrooms with lower average levels of externalizing behaviors. Overall, results here confirmed the previous literature supporting the negative effects of inattentive behaviors and classroom-level externalizing behaviors on the students' academic grades and achievement test scores.