alright i dont know where zurich is but im from the london area and i use to live in ottawa and i was narked on in school once fo a bit of weed

they cut my lock and searched my loacker but didnt find anything (they can do that because its there property) then they took me down to the office and told me to emty my pockets and i refused because they didnt have permission or an officer present

so they asked me to leave, so i did and in the end all i got was a 3 day suspension which i spent smoking the fresh 1/8 i had hidden in the front of my boxers

when its your word against someone elses they cant search you its a breach of your public rights, but the cops can so try and get out of there as fast as you can

but as for your situation you might get a fine but i doubt it, my guess is community service