In Wisconsin you can take them to a driver examiner,they can test them on a car simulator to see how there response is when driving. It is a great test,then they,your son, will also know if he is ready. hope they have something like that where you live.

My brother is ASD and 48 and has been driving since the age of 20. You have to gauge the decision by what he is ready for. I would take him to a big parking lot where there is plenty of room preferably a business that is not open and see how he does