A meta-analytic approach was used to investigate the associations between affective qualities of teacher-student relationships (TSRs) and students' school engagement and achievement. Results were based on 99 studies, including students from preschool to high school. Separate analyses were conducted for positive relationships and engagement (k = 61 studies, N = 88,417 students), negative relationships and engagement (k = 18, N = 5,847), positive relationships and achievement (k = 61, N = 52,718), and negative relationships and achievement (k = 28, N = 18,944). Overall, associations of both positive and negative relationships with engagement were medium to large, whereas associations with achievement were small to medium. Some of these associations were weaker, but still statistically significant, after correction for methodological biases. Overall, stronger effects were found in the higher grades. Nevertheless, the effects of negative relationships were stronger in primary than in secondary school. (Contains 1 note, 5 tables, and 1 figure.)