I'd never heard of this so naturally I had to google -
https://forestschoolassociation.org/Is this the right website?
It appears to be related to teaching children in woodland and forest settings
What do children do at Forest School?A Forest School is a long-term outdoor education process that is holistic and learner-led. It allows children to develop themselves through healthy engagement with risk, problem-solving and self-discovery, all within a natural environment in a hands-on and thoughtful manner