At least a few times I'd get punished myself because they didn't want to even attempt to sort out what had happened for fear of making an error.

This reminds me of one time in early grade school. I skinned my knee during a lunch break and went inside to have it cleaned up. While I was in there something happened outside (I never did find out what), and I guess none of the adults supervising were really paying attention. So they just bulk punished everyone. I had a pretty obvious alibi (I was literally getting bandaged away from everyone else) but once I came back they still punished me too just because they were punishing everyone.

Absolute insanity.