Air filters will be installed in London's most polluted schools as part of a pilot scheme, Sadiq Khan has said.
The Mayor of London said PM2.5 filters would be fitted in 200 schools later this year.
If deemed a success, the filters could be installed in every classroom in London, City Hall said.
Mr Khan said: "I want every single child to breathe clean air in and around their school."
He added: "In those vital early years, the difference to young people's health and well-being can be life-changing."
The pilot is expected to cost £2.7m and forms part of the mayor's 2024/25 budget, which will be voted on by the London Assembly on Thursday.
The funding will pay for the filters and their maintenance, school engagement, educational materials and monitoring the impact of the programme, City Hall said.
Daniel Kebede, general secretary of the National Education Union, said the pilot would be a "massive benefit to pupils and staff in London schools".
He called for the scheme to be "taken up more widely across the country".
Andrea Carneveli, founder of Chiswick Oasis said: "In June 2019, we had the honour of giving Sadiq Khan a tour of our school, St Mary's Catholic School in Chiswick, showcasing the remarkable impact of our newly installed air purifiers, which successfully reduced pollution levels by approximately 94%.
"To see now how 200 schools will be able to follow in our footsteps and provide children with cleaner air to breathe brings immense joy as a parent and fills me with renewed optimism for our future."
City Hall said the schools chosen for the pilot would be spread across London and selected based on pollution levels, as well as those in more deprived areas.
