I have a feeling that as restrictions ease and people take things into their own hands infection rates will rise again so none of this will happen anyway but assuming the alert levels are correct for "the plan" to be implemented, why are yr6 being prioritised?
Apart from some transition stuff they'd be doing mostly fun activities, rather than formal education next half term anyway? Maybe that's the reason to prioritise them, I don't know?
Also, why only primaries to begin with? Phasing things without includjng secondaries at all initially leaves secondaries (mostly) empty unnecessarily? I.e. if it's safe for yr R and yr1 to start a phased return why not also yr10? (or another yr in secondary)