I'm in film studies too, so I'll be harsh, but anyway...
I agree with this guy above...
I'll start with the good things... You had good sound wich was suprising for a high school movie, you had some good shots in general and your plot was kinda good, but refer to the guy I quoted...
On the things you need to work... You need more close up shots in general, I don't know what camera you guys are using, but never ever use the MECANICAL ZOOM it looks really bad. Talking about the zoom, don't zoom/dezoom in the middle of a shot, make another one, closer or further. That said, always shoot close up shots they always come in handy and gives more emotion + you get more into your character (the closer you are, the best the emotions are (if your actors are good))
To know how to film a dialog, just watch a movie where there's 2 guys talking in a restaurant or something like that, and watch how the camera moves around them, and learn, it's basic stuff that you need to know.
And the last thing is, I'm pretty sure you did this with your friends but, don't take a 18 y/o kid to play a chemist, I would of put the old guy as the chemist and put the younger ones as the buyers... Anyway, you guys made a good short if you're starting out!
Keep it up!