The assessment of schools seems to focus mainly on the school's capacity to produce a cadre of academic high performers, see School Rankings. Having worked at RMIT, I remember forming the view that the real test of a school's value was the DIFFERENCE it made (i.e.the value adding) to a student's results, capabilities or resilience. Some schools recruit preferentially or disproportionately from a set of students or socio-economic groups who might already be high performers, or have all the prerequisites for high performance, including external support factors (eg family support, financial resources . . .). Starting with good material and delivering good material is nowhere near as impressive as transforming average students into competent learners or difficult students into capable adults.

I have also been thinking about how to rank schools according to their
atmosphere; ie, is it a happy school or is it a nasty school that damages
the personalities of its students. As far as I know, nobody does this but
it is very important because it influences how social a person is
throughout their life. This is very difficult to measure.