Hello! Please have a look on http://www.osm.org/way/305259283. What is the meaning of the tags 
FEATURE = SCHOOL
OBJECTID = 217713995
Did you know the key unsigned_ref (see https://wiki.openstreetmap.org/wiki/Key:ref).
Please also note that building=school only means that the building looks like a school, but does not have to contain a school (for that amenity=school would be necessary).