It's complicated where the vulnerable and key workers' children are concerned. No personal experience but my DD2 is the DH in a large Primary School. Not all such pupils attend school every day in lockdown, especially where key worker parents work shifts. (eg NHS staff)
They have to liaise with the school over their shifts so that bubbles and teaching staff can be timetabled, leaving other staff to prepare and oversee online work for the larger number working at home. At least one member of staff per Key Stage should be available throughout the teaching day to deal with queries from pupils (probably online).
Where children do not have access to a printer at home, the school prepares work packs for the parents to collect. There is also admin connected with provision of free meals, including (last time) the school kitchen providing food which is delivered by senior staff, if parents can't (or fail to) collect.