Revealed: huge differences in success rates of formerly outstanding schools in Ofsted inspections this term, depending on when they were last inspected

A huge disparity in the proportion of formerly Ofsted-outstanding schools retaining the inspectorate’s top rating, depending on when they were last inspected, is shown up today in an exclusive analysis of official data by this website.

The inspectorate’s rules on what type of inspection schools are to receive, depending on when they were last inspected, seem to have triggered an enormous gap in the final outcomes. This may generate disquiet among school leaders.

My analysis suggests that, among previously outstanding schools whose last full inspection was after the start of September 2015, a staggering 97 per cent have managed to retain the rating following visits from inspectors this term.

However, among schools previously subject to full inspection visits before September 2015, the proportion retaining the outstanding rating was less than 25 per cent.

Primary schools seem particularly affected by this disparity, as my analysis below shows.