Some study done by some guy I don't remember looked at a self-fulfilling prophecy, where a teacher's expectation of a student causes the expectation to come true. The study was done in New Zealand and focused on primary school students of varying ethnicities such as New Zealand European and Maorians. The Maori students were mainly predicted to have a low reading level compared to the other students. At the beginning of the year, the Maori students were at a similar reading level to their peers, but by the end of the year, they had made the least progress. This shows that teachers will keep to their predictions and treat the students to those predictions. In some ways, such as in this study, it can have a negative impact on the students grades.
That wouldn't get me much marks, especially at my size of writing! You need to write half a page, but my writing is below the average size.