Apply for a provisional license, my son did this just to prove his age, he didn't take a driving lesson until well after his 18th birthday! As far as I remember, you need his birth certificate and a reference or personal letter from someone unrelated to him who know him and can verify for his character.
Oh, and remember, there are two parts to the licence - the plastic part which he can carry around to prove his age, and the paper part, which I would advise you to keep safe for him. I lost the paper part, we applied for a new one, and when my son passed his theory test, he left the new one in his shirt pocket and it went through the wash.....Doh!! I made him pay for the second replacement!