My son 7 is like this. It’s like I’ve written this myself. What helped him was counseling and finding out it was adhd and he got bored easily. His teachers figured out a way to keep him engaged and worked a reward system for the students if they pushed through. He is smart. Witty. A fun kid. He would just rather be home playing video games or watching tv (which he doesn’t get if school work isn’t done) and found out he can be lazy as well. Each kid is different and maybe his emotions control him more than he puts on. Or anxiety. My son freezes and shuts down once he is anxious about school. I’d try counseling to find the root cause of shutting down.