It is a state to state issue. This year, my senior year thankfully, they implemented full student drug testing for everyone in sports and extra-curricular activities. Usually, if you belong to anything associated to the school name, even if its just the dang Academic Spelling Group, they can test you if they think you are doing drugs. If you don't belong to anything, no sports or activities, they have to have reasonable cause. Like someone said before, that can just be one of your teachers saying that you sleep too much in class and they want you tested, or someone saying you smell like pot etc etc. Thats reasonable cause to give you a drug test.

The only way you could probably get out of it is if your parent raised hell about it.