I would 1. create an area that delimits the school property, add the Tag:barrier=fence, if any, as hinted by (13 hours ago) TheOddOne2 and add a **new** relation (advanced, multipolygon) to this area with the role "outer" and save to get a relation number 2. create a forest area within a few pixels inside the school property area and add the previously created area with the role "inner"

I would 1. create an area that delimits the school property, add the Tag:barrier=fence, if any, as hinted by (13 hours ago) TheOddOne2 and add a **new** relation to this area with the role "outer" and save to get a relation number 2. create a forest area within a few pixels inside the school property area and add the previously created area with the role "inner"