Studies show that the classroom setting (e.g. pace of teaching) has an effect on students’ level of motivation to doing well in school. Furthermore, recognizing children's potential and working on their individual setbacks can help overall academic achievement. This article states that if a teacher believes the student can do better through additional effort, then the students are more likely to share the same belief and improve as a result.
Source: Blackwell, K. L., Trzesniewski, K. H., & Dweck, C. S. (2007). Child Development, 78(1), 246–263