A letter was received in June 2026 by the Head of Air Quality for the Greater London Authority – Poppy Lyle. 

‘I’m the Head of Air Quality at the Greater London Authority and I wanted to express my sincere thanks to you and your school for your involvement in the Mayor of London’s School Filters Programme. 

I especially wish to thank you for your support with the current period of close monitoring we are doing with your school, including taking calls and facilitating visits to help ensure the filters and monitors are operating correctly.  

This period of close evaluation with your school is crucially important for us in getting robust data to understand how the filters are working, but I’d also like to reassure you that this period of close monitoring is nearly over! The focused evaluation period will conclude at the start of the summer holidays. After this time, monitors will still run, but only so your school can see the data if you wish to – there won’t be any need for such close attention to monitors and filters being on at the right times. 

I appreciate that taking part in the evaluation may have required more staff time and coordination than originally anticipated. Apologies, I know how busy you are, and we are all incredibly grateful for the time you’ve given. 

The information gathered through this monitoring period will help us understand the effectiveness of the filters. This will inform future decisions, and could help bring cleaner air to even more children across London. Early results are positive, and we look forward to sharing findings as the evaluation progresses.
We appreciate your continued support and cooperation over the final few weeks of this evaluation. 

Thank you again for helping us improve air quality for children across London. 

Kind regards, 

Poppy Lyle (Head of Air Quality for The Greater London Authority) ‘