Get dropstuff on the computer (Download it if it's not there)
Open it, hit command-s (stuff), choose the On Guard extension or the preference or whatever (it will let you), check the "Delete files after encoding" check box and stuff it onto the HD or students folder or something.
Restart the computer. No On Guard if you did the extension, a new On Guard if you did the prefs. Do whatever you want. Then, when you're done doing your shit, expand the stuffed file and replace the preference or extension or something.
You just totally by-passed On Guard without being caught.