TLIK, how to apply? On an institutional level, it can seem very overwhelming ie to force every menahel etc to forward these decisions to Rabbonim etc.
But the other way to apply is on a personal level and that is very much doable. The same way many mitzvos are between us and Hashem and as ehrliche yidden, it’s up to us to take them seriously and realise Hashem sees all, so too here. I’m not sure if my principal actually went to a Rav or made those decisions on her own. But because she knew of these principles, they were so much a part of her, that her decisions were very much in line with them and she for sure consulted with others before deciding.
One case when I was in high school was when an out of towner who was dorming in the high school dorm started hanging out with boys. The principal waited till the end of the year and helped her find a different school for the next year.
There was only one other instance of “expelling” I know of (when a group of girls only showed up for the classes they liked and completely disrespected authority with their parents baking. She didn’t accept the ringleaders for the coming year.)
All other other out of the box girls, non academics etc she worked with within the school (she told one girl who was academically challenged that she could make her own schedule of whatever classes she wanted to take in school). So there is much much that can be accomplished by individuals who absorb the proper values.