American legal precedent for this is shit. The supreme court decreed that a public school has the right to search and sieze without probable cause under the general understanding that the school is acting as a temporary surrogate and is responsible for the welfare of the minor in question. You should still deny, though. My lawyer told me that the people in this type of case that he has had the most success in helping have been those that acted like they had never heard the word marijuana. Even a judge (or principal/superintendent) can be sympathetic if they have reason to believe you were taken advantage of. If you aren't in the US, then you're prolly much better off, but a dick faculty can still try to fuck you hard and long. Just tell yourself: I'm good enough, I'm smart enough, and, gosh darnit, people believe me when I lie to their face.