My son is also 12 and has dyslexia and dysgraphia. Things we've found that help with the homework time as well as him not losing the homework before he turns it in is using the computer and emailing the work directly to the teacher. He also does better focusing if he takes 5 minutes every hour to get up and walk around.
Back in 3rd grade, it was the worst. I wanted to go to the school and intervene, because he was doing homework until bed time. My husband, who has the same challenges, stepped in and told me to let my son work it out for himself - that if I made it easier at home, he'd never find alternative approaches that worked for him. Believe it or not, it worked. It took about three months, but he got to the point that it took less and less time.
He still is slow and likely always will be, but he is much faster than he was.
So, to a certain extent, this may be one of those times to squelch the "mommy voice" and let him work through it. It was torture for me, so I know what I'm saying isn't easy.
We've had to learn to balance fighting for accommodations at school so that he isn't left behind in class or put at a disadvantage taking tests, etc. and not intervening at home except in extreme cases like large projects, ridiculously short deadlines on written work, and things that are just physically not going to happen.
Hope this helps. If it doesn't ring true for your case, of course, ignore. What worked for my kid may not work in your case.
