Middle school students' prosocial behavior, classroom engagement, and sense of belonging tend to decline across the school year. This study addressed whether these declines are associated with students' perceptions of their relationship with their teacher and the extent to which their teacher promoted respect among classmates. Self-report surveys were gathered in fall and spring from middle school students (N=351) in low-income, rural communities. Results indicated within-year declines for boys in prosocial behavior, affective engagement, belonging, student-teacher relationships, and teacher promotion of classroom respect; there were smaller to no effects for girls. However, when students perceived improvements in their teacher's social-emotional practices over the school year, they reported increased prosocial behavior, engagement and belonging at the end of the school year. Results were stronger for boys. These results suggest that students' perceptions of their teachers' social-emotional practices can have important implications for their engagement and social development across the school year, especially among boys. Suggestions for classroom-based interventions are discussed. [This is the online version of an article published "The Journal of Experimental Education."]