No, no, no! Absolutely not.
They are incredibly dangerous. Even if your child is extremely responsible and an excellent driver, bad road conditions can create a disaster. My great uncle, a retired city planner - hardly a daredevil, used to ride a motorcycle until he hit a patch of gravel wrong and ended up in the hospital.
That doesn’t even take into account all the other idiot drivers who drive their cars aggressively, under the influence, etc. Even if your child drives perfectly, there is no guarantee that someone else won’t run into them. A motorcycle against a car is badly outmatched and offers no protection to its rider.