t is not the two hours, it is the precedent.
Now any kid who says they had a late night (theatre, concert, sports match finishing late) has a gold plated excuse for coming in late.
There is already a precedent for schools being flexible if a large number of students are going to be affected by an event and adjusting their records accordingly.
Idk if it was just my school but as a child, if you were part of either a school event such as a sports or music competition or an educational trip where the team/group had to travel to the competition venue/theatre/residential site etc and the travel arrangements meant that the students would be returning "late" at night (relative to an average bedtime for that age group) then it was a standing agreement that those children could come in at any time before 3rd period (which would be 10.45am) and they would not be marked as late.
Also if a child was part of a professional theatre/music production and was performing in an event during school term then, as long as the school was aware and had given permission, for the duration of the production there would be flexibility regarding start/finish times for those children. I think they had the same for county/professional sports so for example my friend was called up to the national U16s swim team and occasionally finished early on Friday/came in late on Monday when she had a national weekend competition where she had to travel.
As a teacher, how will you answer the question of why it was ok for the Euros but not for a kid’s away fixture which finished late?
Because school and parents have no control over when the Euro finals are played and therefore have no control over how late their children go to bed (and before anyone starts that you as a parent can send your child to bed regardless of the game, if your child really wants to stay up for the first major men's final appearance by their country in their lifetime, why would you actively punish them by refusing? Thag just sets you up for fsr more issues than an overtired child on Monday).
If you choose to let your child take part in a fixture/competition etc that you know finishes late at night then you either need to liase with the school before the event or accept that your failure of communication is the reason for your child being overtired and not ready to learn. Most schools will be flexible with a late start as long as you communicate beforehand.