You may want to work with your 11 yr old in a practice activity in buttoning shirts and pants. My son eventually overcame this in time. I was so happy and so was he.

Is he in Occupational Therapy because this is a fine motor skill my son worked on with his OT. Worked for him. Just a thought.

Would it be easier to loop a stretch hair tie around the button hole then he can stretch over the button? Maybe it would work until he learns to button.

Velcro