You know what I don't get? If a Sadist Teacher just hates one of his/her students in particular, why not just let the student move up a grade so the student would be out of his/her classroom? Or is the emphasis more on "Sadist", constantly giving the student failing grades just so the Teacher can continue being sadistic?

We don't have an evil bus driver trope?

Removed Professor Mc Gonagall from the Harry Potter section. Mc Gonagall is indubitably a Stern Teacher, but at no point has she ever been a Sadist Teacher.