If you are a perfectionist you can make a stencil, but that limits the size of what you can do. Print up a rat sheet with their names and telephone numbers and distribute it. Get hold of a film to be shown at a school assembly and splice in parts of another movie of your own choosing before the assembly. A little imagination on your part will make for an unforgettable day. Clog up the drains of sinks with clay then turn on the water after everyone leaves school.
Teachers often leave gradebooks, conduct sheets, and attendance records unguarded.
Take every chance to help yourself. Put up posters all around the school. To make them stick permanently use Pet evaporated milk for glue. Carry and pretend to sell oregano rolled in papers and aspirin with the name filed off. Put Calcium Carbide in a gelatin capsule and flush down a toilet or sink.