Can I get your opinion on collective punishment

[ChangeyNameyforthis]

DS, year 8 came home from school upset as his whole class have been given 5 detentions, over 5 days. An incident happened at school with a couple of students and because no one was forthcoming with the info, the whole class is being punished. DS had nothing to do with it, nor did any of the others aside from a couple. The girls have the detention too.

I am not happy about this. If that was your DC would you say something?

I'm a teacher and although I can sympathise with the staff dealing with the incident, this is not the right way to go about it. I would speak to the school about this decision. It's so demoralising for the students not involved. And also doesn't really punish the ones who were as they are not identified.