My son now 13, had the same issue. We had a consistent routine with quiet time and he would go to bed without fuss every night but still be lying there wide awake 5 hours later. Melatonin did not really help, but after moving town and seeing a new doctor, she prescribed clonidine which he takes 1 hour before bed. This medication has changed his life. He is asleep exactly 1 hour after taking the medication every night, and wakes up fresh and rested. His grades have gone up in school and he is generally happier and healthier. It may not be the right thing for your son and you’ll have to discuss with your doctor, but for us, it has been life changing.