PRINCIPALS are demanding urgent clarity about effective safety measures in schools.
Schools closed on Monday for normal business.
However, limited supervision is being provided for children whose parents are key workers and are not in a position to make alternative childcare arrangements.
All pre-school settings and schools are being sent a daily survey to assess how many are open and to how many pupils.
At the start of the week, almost 800 of about 1,100 indicated that they were willing to remain open in the days and weeks to come.
On Tuesday, it is understood that almost 1,200 children were being looked after in almost 600 schools. It is understood around 5,700 teachers and classroom assistants were available to work.
A further 160 school said they would be open in future.
It is not known how accurate these figures are, as many schools might not be reporting to the Department of Education.
The National Association of Head Teachers (NAHT) appealed to parents to only send children to school as a last resort.
"Many families have responded to our appeal not to send their children to school, and we thank them for that," said Geri Cameron, NAHT NI president.
"We continue to encourage all parents who are key workers to seek alternative arrangements for childcare where possible.
"Schools are open for children of key workers that were unable to put in place alternative childcare arrangements and for vulnerable pupils in the coming days."
Ms Cameron added that schools desperately needed clear guidance on how to keep the pupils and staff that continue to attend safe.
"School leaders are crying out for sight of expert medical evidence on safe levels of attendance and density," she said.
"They need practical advice on protective steps they should be taking in schools.
"From masks or other PPE, to distancing children from each other, to sufficient supplies of soap and hand sanitiser, schools urgently need answers to their questions about effective safety measures.
"If re-purposed schools are to remain open in Northern Ireland, the executive must act now to protect our school staff."
Education minister Peter Weir said in these extraordinary times, it was heartening that principals and staff were showing such leadership and compassion for pupils whose parents were key to the Covid-19 response and keeping essential services going.
He asked parents and carers to remember that schools were only open as a last resort option.
"Schools will remain open for staff to allow them to organise remote learning for their pupils and to make provision for supervised learning for vulnerable children and for key workers' children up to the end of Year 10," Mr Weir said.
"I would again stress that parents and carers should only send their child to school if they are a key worker in terms of the overall response to the Covid-19 emergency and have no other viable option for their child's supervision."
