I don't see the issue. Schools these days are routinely understaffed compared to the standards of 25 years ago and their problems escalate as that gets worse. At the same time they are under a great deal more scrutiny and are expected to accommodate more and more variables in their day while being 'fair' and not applying rules arbitrarily.
It seems this school encountered a problem. Instead of expending limited resources making judgment calls and policing a more vague policy, they made a clear, evenly applied rule. That some are upset by this is unsurprising (although I note that there is more hoopla in the press over this than nonsense 'zero tolerance' polices, which are far more egregious).
There are 2 circumstances when you are almost certain to get administrators (of ANY organization) making broad, sweeping policies that are well-meaning but fail to take into account specific situations.
A) neuter the authority to make judgment calls by failing to support the judgment calls that are made
B) when an organization is underfunded, undermanned or under heavy stress
Our litigious society suing over decisions made and unions protecting teachers who make bad decisions has placed schools in the first circumstance and the voters' ongoing obsession with lower taxes and more services without prioritizing public schooling has produced the second.
Adjust your expectations: you will see more and more of these kinds of decisions unless and until we fix those problems.