Me and my mate not a prank well was kinda. Put magnesium into the liquid that makes it bright and firey And knocked it over burnt the floor in the new 1.5 million pound science lab set alarms off ended up everyone on the fierld lol. Didnt mean that was meant to ruin the teachers showing off experiment lol. Good days. You could always cling film the toilets? you could get a fake person dummy type thing. Make it look like someone you hated or something. And hang it from rope somewhere so it looks well you know