There is a fundamental difference between university students and parents.
If a university student skips a lecture they will have to catch up themselves. The lecturer will not disrupt the next lecture to go over the material with them. It is not up to the lecturer to make sure the student catches up. So the other students are not being disrupted. The only person affected by the student's actions is the student. They are not damaging anybody else. And, unlike school, university is not compulsory.
If a parent takes a child out of school for a holiday they are immediately damaging someone else. Their child's education will suffer. Further, when their child returns to school the teacher(s) will be expected to help their child catch up on whatever they missed while they were away, thereby disrupting the rest of the class.
So the two are nowhere near equivalent.
If someone wants to be irresponsible about their own education and doesn't harm anyone else in the process that is entirely up to them. If parents want to be irresponsible about their child's education and disrupt the education of other children in the process I think the government has every right to step in.