Charge them with truancy and fine the parents.
DQ them from extra curricular activities.
If they want to play the civil disobedience card then let them feel what consequences are like and let them see if their “principles” are worth is.
Is the juice worth the squeeze?
This thing with abusing the kids in this manner just irks me to absolutely no end.
This tells me their parents don’t know what is going on with the children. Not just that they are pulling this stunt, but then the kids are going to hold an educational session in the square?