thats great! i hope you get a deserving grade!
i always draw fish, like firsthand observation of my fish, if i can get them up i might post them.
i was also gonne do a huge final piece on fish for my final exam but i couldnt find an artist who did that style cause that was the rule so i did Vartan Malakian (daron from S.o.a.d's dad) but yours kicks the crap out of it!
Yeah, it's hard with art teachers, because they feel they must overlook raw talent (which you clearly have) and grade based upon you complying with exactly what they tell you. Art is tricky ya know.
its a great piece. im an artist myself- but i know what makes the grade is if you follow the requirements. it could be a total turd, but if you fit the requirements you get an A. you have talent, so just blow off the bad criticism.. i think its cool. i would draw some clouds and frame the damn thing lol..