i doubt this will work for you. but we had this exact same scenario. i was tearing my hair out. my very nice, intelligent, generally cooperative child was DOING his friggin' homework and just not turning it in. over and over and over.
i was at my wits' end.
there was no option at that point in time to 'verify that they were done on the nights assigned.' i knew they were. but the teachers were having none of it, and i don't blame them. i'm quite sure they believed me, but their sensible point was that if it didn't get turned in, no credit. bam.
well, it wasn't long after that we made the difficult decision to switch him to private school (and from there moved to homeschooling.) there were several contributing factors, but this was one of them. my very nice child simply couldn't or wouldn't explain this.
he's 29 now. if you ask him about it, he'll laugh and say he was pushing. he wanted to see just how far he could get with them. i wouldn't have believed it then (and not sure i believe it now, but he's still a very nice, cooperative and intelligent person and there's no reason for him to lie about it) as defiance has never been a part of his psyche. but he's always been a curious observer of people, so i guess it does make sense. it's much easier to be all savoir faire about it now. at the time i could have brained him.
in retrospect, i guess i can see rebellion. middle school seemed to be the place where nice ordinary kids got lost in the shuffle. he wasn't brilliant enough to attract college recruiters, learning disabled enough to need intervention, naughty enough to need stern discipline, unruly enough to get sat upon. the teachers liked him, although they usually had to take a moment to shuffle through their mental file boxes to pull him up. he got along with most others (except for some fistfights that i never heard about until he was grown). he stayed after class and cleaned the blackboards, pushed the wheelchairs, helped decorate for dances. he wasn't a showboat. but he also didn't want to disappear. i guess it seemed like a good way for a non-confrontational kid to say 'hey! i'm not just a cog!'
FWIW, he's now very much like his dad. not as neat overall, but very organized in his work habits, very punctual, very well liked and respected at his job, did great in college.
i wouldn't have thought THAT would be the outcome when i was in your shoes.
good luck, hon.
ETA that's him in my profile pic. little cretin.
khairete
S.