The EIS union insisted such a stance was “not an acceptable practice” as it told council education chiefs it would challenge this “legally if required”.
The warning came in a letter to local directors of education with regard to provisions for teachers who had previously been shielding and who are classed as being more vulnerable to coronavirus.
According to the union, 16 per cent of teachers are in Covid-19 “at-risk” categories, while 4 per cent of teachers had been shielding, prior to this being paused at the start of August.
For these staff, individual risk assessments must be updated to take account of the changing picture in the pandemic, with cases increasing again in Scotland.
EIS general secretary Larry Flanagan said it was “simply unacceptable” and a breach of the duty of care councils had to their teachers for risk assessments not to be kept up to date.
He insisted: “Given the rising level of infection across the community, it is essential that local authorities update their individual risk assessments to ensure that the staff in our schools remain safe in their places of work.”
In his letter to education directors, Mr Flanagan said that a failure to review risk assessments would “also be at odds with the advice from Public Health Scotland”.
The union chief went on: “We have heard of some councils requiring vulnerable staff to declare themselves unfit for work rather than accommodating them as working remotely.
“Again, this is not an acceptable practice, which we will challenge, legally if required. Covid-related mitigations and absences should not count as normal sick leave.”
A spokesman for the local government body Cosla stressed that its “main priority is ensuring that the health and safety of everyone within our schools is protected”.
“As agreed with Scottish Government and public health advisers, councils are using a suite of appropriate risk assessment tools to ensure the safety of employees,” he said.
“Where any individual is worried, they should in the first instance contact their line manager to discuss the risk assessment in place for them and they should also contact as appropriate their HR or health and safety team.”
The spokesman added: “Councils will continue to provide a safe education environment for pupils and staff alike in line with scientific advice and national guidance.
“At the the same time, Cosla will continue to work with partners at the national level through the Education Recovery Group.”
A Scottish Government spokesman said: “While staffing arrangements are a matter for local authorities as employers, our guidance makes clear that councils and schools should ensure that risk assessments are in place, including for those at highest clinical risk, and that arrangements enable appropriate physical distancing wherever possible.
“It also makes clear that staff who were formerly shielding should follow advice from their GPs to inform discussions with their employer, trade union and healthcare team on appropriate working arrangements.
“We have provided an occupational risk assessment tool and guidance to support employees and employers when discussing these matters.”