I'd think about your vantage point and how you're framing your shots. In the second one notice the door to the left, it appears that your camera needed to be straight. In the one of the prom queen and king her elbow and his head are slightly cut off and it might have been better to have the photo framed below their waists so arms/hands aren't cut off and so you could see her entire sash w/the lettering.
You don't need the guy in the background in your photo, that makes for a distraction from the subjects - if you could have stepped back and to the left it might have placed the guy in the background behind your subjects and gotten him out of view (or for a posed picture maybe you could have asked them to step to their left to get a better background, or moved yourself farther left and back). It helps if you can make sure everything in your viewfinder is what you want in your picture before you release the shutter, which I think takes time and practice to keep in mind.