I’d be interested to see an example of your use of semi-colons, as in my experience students use them incorrectly more often than not (while thinking they are using them correctly).
Exactly the kind of attitude I’ve encountered when requesting a remark. Oh yes, those stupid little students. Of course they couldn’t use a semi-colon correctly 
FWIW, I was given a ridiculously low mark for a piece of postgraduate writing as part of a course last year. In fact, it was the lowest mark I’d ever got at university, any university, despite being awarded a first in my degree and then receiving a scholarship towards my MA. In a nutshell, I am not stupid! This was the third university I’d studied through and to be honest, I was appalled at the sloppy nature of the lecturers, the lack of attention to detail, assignment titles so vague and ambiguous that it was very difficult to answer any question correctly. I digress...
I messaged the course lecturer and asked her to point out examples of her various criticisms. Apparently my use of English left a lot to be desired. Guess what my other two degrees are in? Yep, languages. She had mistakenly (and not for the first time) awarded my marks to someone else and given me another student’s feedback.
The sad thing about all this was that the university was very keen to back its staff, I was the student and must be wrong, the silly little student who couldn’t cope with not doing well... Categorically not the case and arguably, I was better qualified than at least one of the lecturers due to industry experience. It was only because I was confident enough to challenge the lecturer due to past experience that any of this came out.
What did I take from my latest university experience? Most of the lecturers weren’t very good and would not have survived in the corporate world! They liked fresh faced young students that they could bully and who wouldn’t challenge them, who’d revere their God-like status. When it came to proper intellectual debate and challenge, they crumbled. With hindsight, this was also true when I was a student first time round, it’s just I was too intimidated to complain. Shocking really, given the price students pay for education.