It's a school trip. 
Was planned for First week of summer holidays. Paid for already.
Dds teacher told me at parents evening they're now going to have to go in July because the flights are too expensive in the school holidays. No shit!
I'm not that bothered, I'm sure they don't do too much in the last week or two of term??? But it's kind of ironic.
And yes, I know the teachers don't make the rules about no term time holidays. Ive not taken dd out of school and don't have a problem with that, because ive always understood that school is too important to have a week off.