The Fourth Amendment, they noticed, says individuals shall not be subject to "unreasonable searches and seizures," and this search was flagrantly unreasonable. The mere possibility of finding pills in underpants is not enough, wrote Justice David Souter, to "make the quantum leap from outer clothes and backpacks to exposure of intimate parts."

School administrators might be forgiven for not knowing that. After all, the Supreme Court had previously allowed them to force students to undergo drug testing as a condition of participating in any extracurricular activity. Making students who have done nothing wrong produce a urine sample under the monitoring of a teacher, it insisted, was "not significant" as a breach of privacy.

The court had also permitted schools to search a kid's locker, backpack and purse on even modest suspicion that some trivial school rule had been violated.

Justice John Paul Stevens complained that under these decisions, "a student detained by school officials for questioning, on reasonable suspicion that she has violated a school rule, is entitled to no more protection under the Fourth Amendment than a criminal suspect under custodial arrest." The Constitution's privacy protection, he said, has become "virtually meaningless in the school context."

Stevens did not exaggerate. Even in this case, the court was willing to tolerate making a 13-year-old girl strip to her underwear. It was the "exposure of intimate parts," not the exposure of everything else, that caused the justices to bridle. But if a more dangerous item had been sought or if there had been reason to think she was actually hiding a pill in her bra, the majority indicated, the search might have been perfectly acceptable.

So there's still a difference between the rights we afford students and the rights we afford prison inmates. Just not a very big one.