It looks like you’ve nearly done it - the school is now https://www.openstreetmap.org/relation/8885529#map=17/52.57969/-0.24662 - but there’s an extra bit https://www.openstreetmap.org/way/640502639 that is currently part of the primary school and probably shouldn’t be, and the pre-school also has an extra bit on it https://www.openstreetmap.org/way/403530251 .

The untagged relation that you mention in your changeset comment is https://www.openstreetmap.org/relation/8885531#map=19/52.57956/-0.24648 , by the way. I found that by looking at https://www.openstreetmap.org/changeset/64137949 and scrolling down to “relations” at the left-hand side. I think when you remove the last way from it (which is https://www.openstreetmap.org/way/640502638 ) it’ll get deleted automatically.

Cheers,

Andy