ruling that schools' interest in ridding their campuses of drugs outweighs an individual's right to privacy.
Its not "privacy", its an illegal search. A person's urine is their property.
Congress rejected drugs tests as a condition of their employment. I think ridding Congress of drugs outweighs their privacy too.
For this reason I would oppose mandatory testing of the entire population. These kids have a choice, however. If they don't want to be tested, don't participate in the extracurricular activities.
Extra-curricular activities are not a right, and putting conditions on participation happens all the time. You have to maintain certain GPA levels, etc. It is not an invasion of privacy, because the students have the right to refuse, and they are not denied any of their rights by their refusal - but they may be denied a privilege.