The prom is the last dance at the end of the year, mainly for seniors. (Sometimes juniors are allowed as well, or if they're a senior's date.) It's just a final chance for everyone to have a school dance together before the end of the year. It's more expensive than other school dances because it's not at the school, it's at a separate place just to make it a little more elegant. You usually want to dress up in tuxes or fancy dresses. At regular dances you might wear a simple dress or some dress-pants, but nothing too fancy. I don't have a teenager yet but I do have a son. And yes, I would let him go to the prom in the future. They are 16/17/18 years old when going to the prom and that is a perfectly okay age to be dating. Also, it is a school event, so there are rules and there are chaperones.