At my dd school it's basically 3 behaviour marks then a HT detention.
She has the marks, so now detention.
I haven't spoken to her about it yet as won't see her until later, so don't know what she did. Of course it wasn't her fault.
How do you make them see that it is their fault, it is fair and they should be punished.
Or, have you been the parent that if dc said they were in the wrong place at wrong time and punished for just being there, have challenged the school or teacher.