I think I know how he's feeling. One project can be overwhelming, more than one? Forget about it. Sounds like he's shutting down, which is a rather ineffective coping strategy, but one I still use when my anxiety decides to use me as a punching bag. He might feel like there is no way to get it all done, so might as well give up on getting anything done. Try listing, or giving him a reward for getting through the school day. 'If you get through the whole day, we can go get ice cream as your after school snack'. Talk to his teachers, maybe they can reduce the amount of work required on a project? Finals are probably worrying him the least, just make sure he goes to bed early and has a hearty breakfast.

It's not fun being the parent in this situation, but it's even worse for him. It can literally be hell on earth, and there is a reason this time of year is called 'Hell Week'. When he comes home, let him do whatever he needs to de-stress, if he falls asleep before dinner, make sure you get food into him when he wakes up
(If he doesn't wake up until morning, try to have an early breakfast that he can run out the door with. because the last time he ate might have been breakfast the day before), If he disappears into his room for hours on end, let him, but try to remember to ask him if he wants to do fun stuff, It really sucks to be left out of something because you didn't even know it was happening (ask more than once, he might not register it the first time). It's hard, but try to give him a break at home, even letting his chores go undone (If you are super stressed, being asked to do the dishes is the LAST thing that you want to do) It might make your life harder, but stress is really bad for you if it doesn't get released. Not just mentally, but physically.

It may be that he's too locked onto it to say stop by himself. Ask him if it would be easier if you took the decision away from him. I have some very memorable moments of my mom doing this, and it helped a great deal. Don't force him to drop anything if he doesn't want to, but if it's a mental pressure about making the wrong decision, having someone say that they'll take it out of your hands, and if it goes wrong you can blame them, is an immense relief.

Hope that juggernaut helped