An expert on ventilation and the airborne transmission of Covid says keeping windows open in schools should only be the first step in taking action.
Professor Paul Linden from the University of Cambridge says a combination of measures need to be looked at for each individual classroom.
It comes as teachers call for better ventilation in schools saying the 'open window policy' is unworkable in winter.
Independent research showed that more than a quarter (27 per cent) of teachers work in classrooms where windows cannot be opened.
The government's policy dictates that windows should be opened in classrooms to ventilate the air and purge potential viruses.
Nine in 10 education staff said there was between one and 10 rooms in their school with windows that couldn't be opened.
A quarter (24 per cent) said the policy also causes more viruses due to students and teachers being cold, causing further absenteeism.
More than half of educators (58 per cent) predict there will have to be a return to former measures and disruption if better ventilation and air purification systems aren't put in place.
Professor Paul Linden said: "We know that poor ventilation increases the risk of infection. Covid is spread through airborne particles that can be filtered from the air and removed by introducing more fresh air.
"Opening windows is just the first step, and we have to ask ourselves how practical this is, and how much responsibility we can put on teachers.
"We can't expect teachers to be ventilation experts, so the best answer has to be a combination of solutions that suits each individual classroom".