Traffic noise is a problem for many schools in urban areas — another reason you don’t want to open windows or teach outside.

Moreover, some schools have only small 100% paved outdoor areas.

Example: Ánimo Westside Charter Middle School (funded by Gates Foundation) https://goo.gl/maps/Wn2bu5kkh97Ygqt88

Nearby public elementary school adjacent to nature area, with ample unpaved space, somewhat less noisy, bit still problematic. Playa Vista Elementary https://goo.gl/maps/tydUVn1X9ppB7p699

(Not complaining about charter schools, but this is an interesting juxtaposition, unrelated to the main point of this topic.)