This study examined the effects of first-grade teachers' emotional support on task persistence and academic skills in the sixth grade and the mediational role of children's academic self-concept in these effects. Participants were 524 children (263 boys, X-bar age in the first grade = 7.47 years), their first-grade homeroom teachers (n = 53), and sixth-grade math (n = 34) and literacy (n = 34) teachers. Academic skills were tested, and students' task persistence was reported by teachers in the first and in the sixth grade. Students reported on their academic self-concept and their first-grade teacher's emotional support retrospectively in the sixth grade. First-grade teachers' emotional support had low facilitative effect on children's task persistence in language and math lessons, and it supported reading skills. Teacher's emotional support was related to higher self-concept in reading, and it mediated the effect of emotional support on task persistence and reading skills.