Schools are only required to offer 38 weeks/190 days/1,235 hours of the year to children in Britain. The 13 weeks of school holidays leave 39 weeks leftover for school time so 5 days are for INSETs.
Britain has the shortest Summer holidays I can think of.
They are 9 weeks in Ireland, 10 weeks in Scandinavia, 12 weeks in the Mediterranean and Canada, 14 weeks in USA…
Not all staff who work in schools are paid for 52 weeks’ work a year. I’m term time only plus 15 days. Others are TT+10 or TT+5 or just TT only. Also it’s not ‘Teacher Training’. There can be as many staff in schools who aren’t teachers as are teachers, and these are mainly the staff who don’t work in and aren’t paid for the holidays. The training is for all staff.
And school staff can only take time off during the designated holidays. That includes TT only staff. They can’t decide to go to the Ibiza closing parties in September or Leipzig away for three days if they want to if they’re in school term time.
Schools are not there to look after peoples’ children while they go off to work. It’s not a babysitting service. Children are the responsibility of their parents. Schools are there to offer a set education over a set number of weeks/days/hours. If their parents can’t look after their kids for the rest of the time that’s their problem.