not sure how this works in the u.s but in england being a drug user is not illegal, but possesion and supply is, my idea is dont take any shit to school, then you can only be caught by the cops, and they need grounds to search you, if they want to test you tell them it is your right to say no and they have to respect it, you amy get suspended but not as bad as being caught
Refuse the Test . ask for proof of charge. threat them with a lawyer or lawsuit. you uncle is a jewish lawyer.