@onedayinthefuture - holidays could be sorted by just paying teachers to work those dates. (They arent currently paid for them and if you want teachers to supervise key worker children in the gap now, you do need to pay them to work in the summer, most people are prepared to work their days off in an emergency, but also expect to pay paid for them).
Bigger issue is the exams. There needs to be a gap between taking exams, the exam boards marking them, issuing exam results and then students moving on to the next course. (Ie GCSE to A level or other qualification at year 12, often not at the same school)
So the exams would have to stay as they are to give time to get the results back. The gap now would just mean those students went into the exam with fewer weeks of education.
It might work at primary level. Can't see it being popular if we've all had the vaccine by the summer but still can't go on holiday because the kids are in school through August and starting the new school year in September.