Glasgow City Council opening secondary schools while support staff are taking strike action is “abhorrent”, the country’s biggest teaching union has said.

Staff including support assistants, catering staff and cleaners from Unite, Unison and GMB will walk out next week across the country as part of action on local authority pay.

Glasgow support staff will strike between September 6 and 8, with all primary schools set to be shut.

But the local association of the Educational Institute of Scotland (EIS) has hit out at the decision to open secondary schools.

Susan Quinn, the secretary of the local association in Glasgow, said the union was “firmly in support” of the action being taken, adding: “Schools cannot, and should not, be operating with only teachers present.

“This is dangerous and does not provide a suitable learning environment.

“It is abhorrent that the council should think it appropriate to open secondary schools without the appropriate and relevant support staff.

“Other local authorities are taking a less antagonistic approach by closing schools to pupils and teachers on strike days in the interests of protecting their health and safety.”

Ms Quinn said there had been reports of headteachers in the city being told to reject parental leave for teachers in all but “extreme exceptional” circumstances, while marking teachers who call in sick during the walk outs as having taken illegal strike action.

“It is a further example of poor industrial relations in the council that they are now taking, in effect, secondary action against teaching staff by restricting their terms and conditions during industrial action which they cannot lawfully participate in, according to UK government anti-union legislation,” she added.

“If our members cannot legally take strike action because they haven’t been balloted (yet), how can the council use other unions’ strike ballots to cancel sick leave and parental leave for teachers?

“Worst, perhaps, of all is that we know this instruction is verbal to headteachers and in direct contravention of written guidance which has been issued.

“We believe this to be a breach of terms and conditions and potentially discriminatory.”

“We are emailing advice to our members across Glasgow with the EIS position on what to do during strike days.

“This will include considerations around health and safety of staff and our children and young people, childcare arrangements, and solidarity actions with our sister unions.”