This boy was neglected by his own family. He was probably told that he is stupid and useless. He needs someone to help him get his self respect.
You can tell him that he is smart, good and needed. You can ask him to help you and after he does thank him, make it a big deal. Find a kid that needs help with reading and ask him to read to this kid.
Get him to read a lot, any book for his age.
Get your son to involve him in sports at school.
Don’t tell him what is wrong with him; tell him what is good in him.
Thank you for caring. All kids deserve to be loved.