Headteachers are calling for clarity on whether schools will be expected to open to a limited number of pupils over half-term, to avoid "weeks of government dithering" before the holiday.
But the Association of School and College Leaders (ASCL) has argued that schools should not carry the burden of planning half-term provision if the decision is taken to keep vulnerable and key worker children on-site.
It should be the job of local authorities to coordinate provision for these pupils in the event schools are required to stay open over the break, the union said.
Gavin Williamson: Teachers to get two weeks' notice of school reopenings
End of lockdown: Regional approach to school openings 'likely'
Julie McCulloch, ASCL's director of policy, strongly urged ministers against further adding to school workload with an "extra expectation over half-term".
Coronavirus: Schools 'should not have to plan half-term provision'
"The government has yet to confirm whether or not schools will be asked to put on some provision for vulnerable and key worker children over the February half-term holiday, as happened over holiday periods in the first lockdown," she said.
"We recognise that, depending on what happens with infection rates over the next few weeks, there could be a need for some limited provision during half-term for a small number of children of our most critical workers. If this provision is needed, it is our view that it should be coordinated by local authorities, and not landed directly on schools.
"The pressure on school leaders and their staff has been relentless since the pandemic began, and they have spent months juggling remote education, in-school teaching, contact tracing and managing safety processes.
"The government cannot keep giving them additional responsibilities, and we strongly urge ministers against further adding to workload with an extra expectation over half-term. This needs to be sorted out soon so that everybody has clarity and we don't have weeks of government dithering."
The Department for Education has been approached for comment.