I think that is not surprising, I have always been on good terms with teachers because I couldn't discuss things with my peers since they didn't give a damn about anything, so I "talked" through my writing with the teachers and especially language, sociology, history teachers seems to like it.
I have always been open to discussion, but I never start a talk because of some sort of trauma (there is so much to say, that I would be talking for longer than I should). Thus my only way to express my opinion was through writing (or talking if someone asked, but this situation is pretty uncommon, unfortunately) and since I do it most of the time in school time, it is not surprising that some teachers have taken liking of me.
That is natural, what else could a teacher ask, if not for a student who shows strong opinion, which may be interpreted as interest, in what they are teaching?
I believe grades have nothing to do with that, but my opinion might be biased, since I have never had any problems with my marks... Summing all my marks and dividing by the number of subjects would probably result in a B (?*) most of the time.
Well, I may be lucky because my school is not so strict about homework, so there is actually no problem if you do not do anything besides the tests and one or two bimester projects... Meaning that if you do only the tests you probably will score C or B plus these projects (summing to A). This would be perfect, if you were not held a class for being absent 25% of your stipulated school time.
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*In my country scoring is from 0 to 10, where 6 is average, I am not sure about this E, D, C, B, A stuff, but I am guessing that B is from 8 to 9 or 8,5 to 9 and A is greater than 9.