Don’t dress like you’re running for prom queen (or king.) Especially if you’re over 25. Put that hot pink prom dress or that cheesy blue tuxedo back in the closet. Go conservative. Remember that you are representing the school when you chaperone a prom. There is nothing wrong with wanting to look and feel great, but don’t do it at the cost of ruining the night for the kids there. Even if you missed your own senior prom, does that really make it right to steal their night to try to make up for it?
Decide whether it’s appropriate to follow the prom theme. Just because the theme is “Adventures Under the Sea” doesn’t mean you should show up dressed as a mermaid. If the chaperones have decided as a group to dress in theme, then you’re OK, but if not, you will most likely regret your decision the moment you walk in the door.
When in doubt, go the conservative route. The only thing more embarrassing than seeing that one woman dressed in a hot pink ball gown is BEING that woman. Go conservative - you can still look nice, just don’t steal their moment. Maybe a conservative little black dress or something classic in a springy color scheme. If the kids will be in formal wear, then you should too, but keep it under control.