The Association of Secondary Teachers, Ireland (ASTI) has defended the decision to ballot its members for industrial action, with union members saying if a safe environment can't be provided, teachers and students should not be in school.
The union signalled its intention to ballot members over potential strike action amid fears about health and safety in schools. There are concerns about PPE and high-risk staff working in such an environment.
Teachers who are at high risk from Covid-19, or teachers and students living with high-risk family members, are concerned about their health, according to ASTI president Ann Piggott.
"We have teachers who are very worried about their own safety and the safety of their loved ones," she said.
"This motion says we will ballot our members, up to industrial action. Nothing is ruled in or out. That will be decided by our members, but we would like these issues addressed by October 30."
Other unions have warned that cases of Covid-19 are likely to rise due to the number of students in classrooms.
John Boyle, general secretary of the Irish National Teachers' Organisation (INTO), said it has been contacted by principals who took contact tracing into their own hands because they believed the HSE was not moving quickly enough.
"The principals are pulling their hair out. They know they have a confirmed case, the parent has rang in to say the child is positive, yet the HSE has not made contact with the close contacts yet," said Mr Boyle.
"Eventually the principal gets through to the HSE, who tells them they are snowed under and don't have the staff, and they ask the principal nicely to ring them. Then the principal, who is not a health expert, is telling people to not come in."
Richard Terry, a history and maths teacher in St Colman's College in Fermoy and a member of ASTI, said years of under-investment has led to these Covid safety concerns.
"Because of poor teacher supply, there is greater pressure to keep teachers in classrooms even if they have been in contact with a confirmed case in school.
"Class sizes are a problem due to the lack of teachers, as well as the lack of space for [more classes]. A lot of our infrastructure is old, poorly ventilated and poorly insulated."
Sean O'Riordan, director of the National Parents Council Post Primary, agreed that a fast-track testing system is needed in order to keep the schools open.
"No parent wants teachers working in an unsafe environment. Unless we have comprehensive testing and quick turnaround, we have no idea where this virus is," said Mr O'Riordan.
"As for teachers with underlying conditions, you would also have to be concerned about them."
The Department of Education said an enhanced occupational healthcare service has been put in place to categorise staff into one of three Covid-19 risk categories.
"This is in line with the approach being adopted in other areas of the public sector including the health sector," said a spokesperson.
"Staff in the normal and higher risk categories can return to the workplace, provided appropriate risk mitigation are in place and implemented according to their School Covid 19 Response plan. A review process has been put in place where concerns remain."
The department said it will continue to engage with all education partners, including ASTI, in the coming months.
The HSE did not supply a comment before the time of publication.