Teacher-student relationships are an important part of students' interpersonal context at school that impacts their academic development. This study extended prior research into teacher-student relationships by exploring the relative balance of negative and positive teacher-student relationships in high school students' academic lives (in each of English, mathematics, science, history, and geography subjects). Also examined was the role of this relational balance in predicting students' school engagement (operationalized by academic participation, enjoyment, and aspirations). The study involved a longitudinal sample of 2,079 students from 18 high schools. Findings identified a significant linear (main) effect, with an increase in the number of positive relationships (relative to negative relationships) with teachers predicting greater school engagement. This was accompanied by a significant curvilinear effect. Specifically, (a) when the relational balance became predominantly negative, students' engagement was lower, but did not decline with an increasing number of negative teacher-student relationships, and (b) when the relational balance became predominantly positive, students' engagement was higher and became increasingly more so as the number of positive teacher-student relationships outnumbered the negative. We conclude that the enhancing properties of positive teacher-student relationships seem to outweigh the limiting (or narrowing) properties of negative teacher-student relationships. Further, there is cumulative engagement yield through increasing the number of positive teacher-student relationships across students' school subjects.