[dpark]

Minors have largely the same rights as adults. There are reasonable restrictions on those rights, but the default is not "no rights with a few exceptions". It's "all rights with a few exceptions". For example, schools are allowed to place some restrictions on students' speech, but they cannot forbid speech unreasonably (e.g. cannot require pledge of allegiance; could not force students to remove black armbands protesting Vietnam War).

And no one said the school can't ask about drug use. But the students can refuse to answer.