One kid pulled that “you can’t do that” to me once when I grabbed his arm as he was punching another kid. Quietly told him I was protecting myself from his fist and for him to prove otherwise. Another time I paused by a bully and whispered a little something-something and that was the end of that. It has to do with respect as I’d lose a fight with a fly. I quit 5 years ago because the kids were getting worse every year. 100% the parents’ fault.
Yep-my husband replied with something to that effect. He is pretty sure his days as an old school kind of teacher are numbered.