Is it normal that my headmaster won't let us have time off to go to glastonbury

I went last year to Glastonbury, as a big music fan, but we had to write to get permission. We asked if we could go. He said no. We went anyway, claiming that it is a health and satfey hazard not going a day early or else we would have to pitch tents in the dark where we could trip over and hurt outselves- a valid point i thought. We got a bullshitty letter back saying "its not acceptable, you mustnt let it happen again" and wrote in our news letter that no one under any cercumstances may leave to go to glastonbury. This year im just going to be ill. I was just wondering if it was normal and happened in other schools too?