Thousands of carbon dioxide monitoring units will be deployed under the plan and high-efficiency particulate absorbing (HEPA) air filters will be installed in spaces with insufficient airflow.

"The way in which airflow works in school spaces is incredibly important in terms of containing, and hopefully limiting, the number of infections in any school-based environment," Premier Daniel Andrews told reporters on Friday.

It's expected a plan for students to return to the classroom for the start of term four will be announced next week.

Mr Andrews said he could not yet provide the full details of the air testing program, but promised plans were well advanced.

"There will come a time in term four when school is back in the classroom, and everybody is a risk to everybody else," he said.

He also flagged outdoor classrooms could be used to reduce the risk of virus transmission, along with rapid antigen testing once the Therapeutic Goods Administration approves them to be self-administered.

"It may well be applicable, logical, that we use some of that rapid antigen testing - self-administered - as part of our return to the classroom," Mr Andrews said.

The state opposition has been calling for rapid tests to be rolled out in certain settings for weeks and criticised the delay.

"If Daniel Andrews hadn't been so dismissive of our suggestion, then we could have had kids back in school face-to-face at this really critical moment," opposition health spokeswoman Georgie Crozier said.

Children are believed to be a particular transmission risk for the Delta variant, with no vaccine yet approved for those aged under 12.

Meanwhile, a vaccination blitz for VCE students will begin next week to ensure students sitting exams have had at least one jab dose.

Students will be given priority vaccine access to get their first dose of Pfizer, with appointments available from Monday.

The priority access is expected to cover 60,000 to 70,000 Year 12 and 11 students sitting 3/4 exams, as well as their teachers and examiners.

The state government wants all Year 12 students vaccinated with at least one dose by October 5, the date for the General Achievement Test, which has been rescheduled several times.

Vaccination hubs will be set up at several schools, including Gladstone Park Secondary College, Roxburgh College, Point Cook Secondary, Lakeview Senior College and Dandenong High School.

Mr Andrews said he did not know how many of the state's teachers had been vaccinated, and had not considered whether unvaccinated teachers should be allowed in classrooms.

Australian Associated Press