From what I’ve read (supposedly quoting statements from parents whos kids were excluded) was that they were willing to do everything the stricter school wanted, and the school didn’t want them.
completely untrue. They were not at all willing. Besides the fact that those families brought this to a secular court instead of Beis Din is quite a clear indication of their unwillingness to abide by basic Halachah, let alone a frum lifestyle (no TV, etc)