Wants to be a pilot does he? Yes you are in trouble madam. Try not steer him away from it, as he may get worse. Try and encourage him a little then try and get someone to show you and him, the results of the broken dreams, the carnage, the broken marriages. Women just dont understand aviation! Etc., etc.
In all seriousness the greatest asset he can have is the drive and determination. If he has that he will get there, one way or other. Good fun for a while but if he is after money he wont make a lot but it beats working for a living
Tell him to stay at school and further his eduction, then have a go at the military route. If he dont make it there, take the other route of course.