And: your judgment is that hypocrisy is the worst sin. Is this Lutheran doctrine? And the reason why a Lutheran school should be required to be run according to Accygirl doctrines is because...?
Third point: If these girls were concerned about their privacy, dang, I just can't understand why they would be showing offensive pictures of themselves around the school. And double dang: now they're bringing a lawsuit against the school, with a great fanfare in the press. By the evidence: are they avoiding, or seeking publicity?
An opinion with which many of us disagree, and which is incoherent in view of your contention that only the "morally pure" may judge. (How "morally pure are you? How do we know that you aren't a hypocrite?) And why is your opinion worthy of greater respect than anyone else's?
Unless they're expelling all the students who are having sex, which I very much doubt they are, the principal has no right to expel the girls.
Got an experiment for you. Next time you're stopped for speeding, explain to the nice patrolman that lots of other cars were speeding too at the same time all over the USA, and he doesn't really have the right to ticket you for speeding if he's not going to ticket them.
While he's laughing at you, you can think about how ridiculous your contention is.