My opinion is probably controversial and people will hate me for it, but here goes.
I think it's worse for the current Y10 and Y12 students than it is for Year 11 and Year 13, who at least were at the very end of their courses and therefore a reliable, evidence-based teacher-predicted grade was relatively easy to produce (I have a child in Year 11, and a husband who teaches both Y11 and Y13).
The current Y10 and Y12 students are, I think, pretty f**d tbh
. I think it's too late to salvage things for them. Even if they can go back to school on 1st June, how on earth will their classes actually be managed? You'd only be able to have a few students in each classroom. In core subjects (Maths, English, Science etc) you simply wouldn't have enough teachers to teach them all at once, given how spaced out they would need to be (and let's not even get started on the fact that within each year group in year 10 there will be different academic streams or sets) ... so inevitably the students would be in school part-time, with the teachers repeating the same lessons over and over again to different groups of students. I just don't see how it can work.
I think Year 10 and Year 12 should study at home with as much remote teacher input as possible, with the expectation that their final grades will be allocated by the teachers in the same way that Year 11 and Year 13 have been, but obviously with an absolutely massive allowance made for all the education they will have missed.
Year 9 and 11 should be the priority now ... they have 2 years to go until they sit GCSEs and A Levels, so we have time to make sure they are as unaffected as possible.
Re primary schools: I think Years 4 and 5 should take priority over Year 6.