This is as much effort as I'm willing to put in, but you were probably right to be sceptical; it seems unlikely to be zero.
See also: Pygmalion in the Classroom.
Simply put, when teachers expect students to do well and show intellectual growth, they do; when teachers do not have such expectations, performance and growth are not so encouraged and may in fact be discouraged in a variety of ways
It's entirely reasonable that teacher's ratings of children's academic abilities &tc cause future achievement.
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