The only for sure is that it doesn't eliminate due process and procedural safeguards. My concern on both sides (one more than the other) is due process got mangled, now it's down to facts about allergy. Disability is less on trial than allergy itself, which is more or less what your point was.
The lesson here, I think, is come preloaded with indisputable and more than sufficient evidence of qualification then stay on track even if things take a turn to wherever this went. I'm going to make the unpopular suggestion that the flyers directly to other parents in class wasn't protected because it was outside of process or procedure. The lack of justification or reason in the principle's choice of actions not withstanding.
But yeah, I'm kinda thinking allergy as a hidden, episodic disability is on trial and the associated perception helicopter parenting, MBP. Perfect storm, perhaps.