damn that blows. my schools pretty low key- its an unspoken agreement that all the stoners will smoke weed regardless, so as long as its not blatantly obvious, or disturbing somebody, nobody really says shit. i started smoking weed in like the end of 7th grade, and back then everyone was still under the reefer madness spell, and i got called down to the office and searched by the police/principal like 20 times up until the 10th grade. i never had shit on me though, so it was all good. but yeah, (most) people have grown up now and dont even give shit enough to narc- most people who used to be snitchin are now blazin themselves anyways. besides, we keep our shit pretty quiet anyways. but yeah i agree, fuck narcs...
I wouldnt get bent out of shape over this shit, they've been doing it for a while. I even have a buddy that did that kind of work for the cops, help busted parties and shit. Just be smart and dont bring shit to school and you'll be perfectly fine.
Find out who they are and print up anonymous banners revealing their identities, with a bulleted list of their duties and 'busts' they have been partially responsible for. Put them everywhere. Let justice prevail.