It may be that he has good ideas but slow/poor writing doesn't let him get things down properly - letting him use a medium he finds easier would boost his confidence. Or, as MrsW says he's doing a specific programme to help an area he's strugling with. Either way you do need to ask!
It sounds like his self esteem is starting to slide and I would really urge you to try and deal with that - point out all the things he is good at etc. My (now 15 yo) DS1 wasn't assessed as dyslexic until Y6 and it had a huge impact on his self confidence as he struggled with things his peers fround easy. Even now, although he is doing well at school, his starting position when he can't do something is "I'm thick" which is heartbreaking.