This study investigated the construct validity of measures of teacher–student support in a sample of 709 ethnically diverse 2nd- and 3rd-grade academically at-risk students. Confirmatory factor analysis investigated the convergent and discriminant validities of teacher, child, and peer reports of teacher–student support and child conduct problems. Results supported the convergent and discriminant validity of scores on the measures. Peer reports accounted for the largest proportion of trait variance and nonsignificant method variance. Child reports accounted for the smallest proportion of trait variance and the largest method variance. A model with 2 latent factors provided a better fit to the data than a model with 1 factor, providing further evidence of the discriminant validity of measures of teacher–student support. Implications for research, policy, and practice are discussed.