MAY is the key word.
But if I had to put money on it, I would say year 6 will return from June 1st and the speculation is right.
Purely from the point of view that its becoming increasingly untenable to keep primary school kids off and year 6 is such a crucial year.There is growing evidence to suggest that 10 and 11 year olds don't catch the disease and spread it as easily as adults and older children.
I don't think it can be earlier than that because the schools won't be ready for it and I don't think it can be later than that as otherwise we are running into the school holidays. (And my suspicion is that they want to keep the option of being open over the summer, on the table too).
They will want to have some distancing at least initially to see if the R rate increases and they can't do that if all the kids are in, so staggered restart with year 6 in first makes most sense. They will be guinea pigs for other years.
The reason it isn't year 10 and 11 is because they are more concerned about older children spreading the disease.
The alternative is no school til September which will hurt parents who are juggling childcare and work even further.
Yes its speculation, but the reasoning about the timing being around a week either side of 1st June is sensible and difficult to argue with.