Yes, some pretty classic patterns here - I would definitely agree that assessment would be helpful. Something beyond his control is getting in the way, and it's having negative impact on how he sees himself, as well as his school work.
It could be ADHD and/or some other kind of learning issue that's affecting information retrieval, reading or writing. If you know what's getting in the way, he can start figuring out what he needs to do differently in order to be able to do well. I would be prepared to find he's got a lot of anxiety, and a lot of resistance to change, if he's ingrained the idea that "I am not good at this". For us, digging the poor kid out of the deep anxiety hole they're in is always the hardest part.
Also worth noting: 2E kids can be really good at compensating and hiding their issues, so you may have to do some serious searching to find a psych that knows how to look for these challenges in a PG child.
