Some teachers are dramatically more effective than others but traditional indicators of competence (e.g. certification) explain minimal variance in performance. The rigors of teaching suggest that positive traits that buffer against adversity might contribute to teacher effectiveness. In this prospective longitudinal study novice teachers (N = 390) placed in under-resourced public schools completed measures of optimistic explanatory style grit and life satisfaction prior to the school year. At the conclusion of the school year teacher effectiveness was measured in terms of the academic gains of students. All three positive traits individually predicted teacher performance. When entered simultaneously however only grit and life satisfaction remained significant predictors. These findings suggest that positive traits should be considered in the selection and training of teachers.