You could make a LaunchDaemon that runs each time the system is booted.
Example script (from another question):
for user in $( ls /Users ); do
if [[ "$user" != "<someadmin>" || "$user" != "<someotheradmin>" ]]; then
rm -rf "/Users/$user"
If you merely use the example script above and call it from a LaunchDaemon, it will erase the users' data (except for "someadmin" and "someotheradmin") each time OS X starts up, but their account will still be on the system. This means that the students could still log in, but their home folder would be recreated each time they logged in.
To remove users from OS X's directory (either local accounts or mobile accounts from a networked directory), use dscl:
dscl . -delete "/Users/$user". Add that line right after the
rm -rf. Depending on your directory, more investigation might be necessary. :)