Suppose the principal had been a male, instead of a female -- would the same behavior have been equally acceptable? If you say, "yes" -- you will be viewed as a pervert. If you say, "no" -- you will be viewed as sexist.
The answer is -- the principal's behavior was unacceptable and the case is actionable in a court of law. It's a clear violation of the 4th Amendment. It constitutes an illegal search and a violation of privacy rights.
LOL ! !
what's the old saying about 'enough rope' ??
We're not playing "suppose" here; we're talking about a specific, individual case. Your hypothetical is only a hypothetical.
The answer is -- the principal's behavior was unacceptable and the case is actionable in a court of law. It's a clear violation of the 4th Amendment. It constitutes an illegal search and a violation of privacy rights.
You've got your personal opinion and nothing else---no law, no precedent, nothing. All USSC precedent, in fact, seems to suggest the exactly opposite of what you think is right.