I can tell you that a university education is no guarantee for the reliability of correct grammar. I once had a teacher in German. She was Norwegian, and told that there were things in German she could NOT write because it sounded too Norwegian. But I who had no such University exams, but who had read a lot of German, could actually prove her wrong. The case is that we have received much of our construction of words from German, and many patterns are the same, though the language is different. If the teacher has not managed to connect the languages in this way, or to see paralelles in those two languages, the way to mistakes is short. When the teacher says this and that it should be possible to make an argument, and show the teacher by demonstration the difference between "porter" and "s'habiller".