Childhood is a critical period for the acquisition of healthy behaviors, and the promotion of sustainable healthy behavior among children is greatly important. Therefore, an increased understanding of the relationship between grit and physical activity in a school context is needed. The purpose of this study is to describe and develop an understanding of students’ and teachers’ awareness and experiences concerning grit as a health-promoting factor. Fifty-five students and three teachers participated in the study. Data were collected through the Short Grit Scale and focus group interviews. There were weak to non-significant correlations between the three teachers’ ratings of their students’ grit and the children’s own ratings. The qualitative results show that children and teachers understood the construct of grit but had slightly different perceptions of it and that grit is not considered to be set in stone. The participants made an association between grit, motivation, meaningfulness, and setting goals. The findings indicate that grit might be an ideal target for making physical activity interventions sustainable.