Definately not. Young drivers are very subject to having auto accidents. It is way too easy for the M3 to exceed his driving experience, school or no school. That car can easily turn around and bite him.
Be truthful with him and tell him what you were thinking when you told him about your car purchase thoughts. Don't give in to him just because he wants it now, you're own instincts seem to say that the M3 is too much car, so just be truthful.
Maybe it might make a good college graduation gift, but please, get him something safer to drive.
A 56 year old Dad.