Nicola Sturgeon has pushed for a more “grown-up” discussion of school ventilation after proposals to amend classroom doors were met with derision.

Opposition politicians attacked the Scottish Government for the plans, which is hoped to stop the spread of Covid-19.

In a letter to Holyrood’s Education, Children and Young People Committee on Wednesday, the Education Secretary, Shirley-Anne Somerville, said about 2,000 classes needed improved ventilation across Scotland at an estimated cost of £4.3 million.

The funding will be paid out by a £5 million increase in capital funding for schools paid to councils.

Air filters and mechanical fans, at a cost of £1.6 million and £2.4 million respectively, would be employed – along with £300,000 spent to “undercut” doors, which was seized on by opposition politicians.

At First Minister’s Questions, Tory leader, Douglas Ross, said: “The Covid pandemic began more than two years ago, the Scottish Government has had all that time to make our schools fit for use.

“Why then First Minister are we in the position, after all this time, that one of your Government’s ideas to protect kids and teachers is to chop the bottom off of classroom doors?”

The First Minister said schools “are fit for use”, adding: “The Scottish Government continues to take a range of measures to ensure that children and staff working in schools are as safe as it is possible for them to be.

“One of those measures, of course, is one that Douglas Ross – against all logic and most expert evidence – opposes, which is asking staff and pupils in our secondary schools to wear face coverings.”

The First Minister went on to say there were “a number of things” that can be done to improve indoor ventilation.

“Partly, that can be about air filtration to purify the air, partly that is about ventilation, so mechanical ventilation systems, but also partly, and this is the key point, it’s about taking measures to ensure that the natural flow of air in a room is maximised,” she said.

“If you have doors or windows that are not enabling that natural flow of air in a way that you would want it to, then it would strike me as basic common sense you would take measures to rectify that.

“What we’ve done is give additional money to local authorities to allow them to take whatever steps – air filtration systems, mechanical ventilation or basic rectification of the structure of classrooms – to improve the natural flow of air.”

She added: “That strikes me as basic common sense and if Douglas Ross wants to have serious discussions about these matters then perhaps he could start by making sure it’s a grown-up discussion.”

The Tory leader also asked if the Scottish Government had engaged with the fire service about the safety of amending doors, claiming a retired fire officer had told him the changes may be unsafe.

The First Minister said that consideration would be for local authorities.