I got a passable grade in Linguinstics, I just managed to scrape through a grade of 6 (or 60% if you wish).
I left out the "professor" information, no point in making it responsible for the mark. Other point to notice is that the verb "deu" in Portuguese may suggest a paternalistic streak (language-related, I mean).
Professor, because I suppose you mean University studies, since Linguistics certainly isn´t a high school subject. Unless I am mistaken.