It's not irony. It's about learning to submit to the will of the system. They know full well what they are doing. They are getting you used to idea that they are in control during school hours.
When ever I used to take my son out of school early they would ask what's the reason? I would say because I want to. They didn't like it but they had no choice. I could tell they wanted a real reason - something they could put in the books so as not to lose money for the day.
I’ve noticed the pattern of calling parents AFTER 10 AM to pick up kids, when attendance is taken and thus education funds secured.