I think it's unfair for the teachers to try and teach in a classroom where some students are under the effects of drugs. I think tests are fair for them. Parents often don't listen and take the part of their children, being too blind to see what's really going on. If the teacher has evidence the student is doing drugs the thing works much better.

I don't care about privacy in this instance. It deals with minors, and the fact that minors are going to school after taking drugs actually scares me.