This is the latest graph breaking down infections by age group. Unfortunately, it's already two weeks out of date, but show very clearly that the steepest rise is amongst secondary pupils.
The vaccine will do nothing to stop that. The only solution is to stop pupils in the most infected areas from contact.
There is almost nowhere in the country now with a daily infection rate below 20 in 100,000, which is 1 in 5,000. That means in a secondary school of 2,000, there could be two new cases every week. Some areas are, of course, much higher.