For a reasonable price the Octava MC 012. After trying it and comparing it to other mics before, this was my choice to my own studio. It's great for other recording situations too....get a stereo pair and you can record what ever you want with it.
I often use the Neumann KM 84 or KM 140 on hats. But I have discovered that a RE-20 (EV) or even a MD421 with some compression gives me a really tight open hi-hat sound that works well for harder music. Try both the 57 and the 81. The 81 will probably give you a crispier sound than the 57.
We don't have the 012 here but the PA company I work for has two of them. I haven't had the time to try them yet. If I get the chance to compare the 012 to other mics I will let you know.
Guess you have a lot of mics around at the school.