Time to chill, daddyo! (or rather, mommyo. . .)
Your snake is probably fine, and I wouldn't be too hard on your son. Tagged or not, hatchlings have a tendency to make seemingly suicidal leaps to freedom from people's hands and be perfectly fine. Many a careful adult and experienced breeder has dropped a hyperactive hatchling no matter how careful they were being.
If your snake tends toward tagging, instead of making your son paranoid about dropping it, I would encourage him to handle the snake MORE often. The more a snake is handled the friendlier and calmer it becomes, and most hatchlings can be trained out of being nippy just by being handled every day. Occasionally dropping a snake from the height of a person's hands probably won't hurt the snake, and it is bound to happen from time to time, even to people being careful and experienced adult handlers. This should not prevent you or your son from handling the snake as often as you like. The positive effects of regular handling for a pet snake far outweigh the minimal risk of occasionally dropping it on the floor.
I've seen snakes fall off of kitchen shelves and fall almost six feet to the linoleum and be perfectly fine. Unless your snake is showing other negative symptoms, it's fine and should be treated and handled normally.
Cut your son some slack. It happens to everyone!
My 2 cents,
Jamie Lynn