I'm just curious, what impression does my outfit give?

Cute and casual. For prom you want a little bit more magical. Shoes look good. At your age you can probably still work this outfit without major issues. However as you are going to college soon I suggest changing to a more age appropriate less conservative and form fitting combination. The problem with this outfit is it screams sultry dominatrix but I doubt that's your goal. Also black tends to fade faster as a color so consider updating the outfit anyway