“However, we note that it has taken an unusually long time to publish the outcomes of research started in September 2015. A small number of primary schools (26 in total) were involved in the research and this sample was further constricted by the fact that all the schools involved were previously judged as good.
“In reality, away from the constraints of research methodology, inspectors are called upon to make much more complex judgements.
“In secondary schools, where a greater range of subjects are taught, inspectors have to make an overall judgement of the quality of a whole school. Given that there is much greater variation in teaching quality within schools than between schools, ATL questions how valid and reliable these inspection judgements really are.
“Unfortunately, the long-delayed results of this study provides no answer to this key question.
“The time is overdue for an independent investigation of Ofsted. The question must be answered: does Ofsted inspect schools in different areas, with different social intakes, fairly? Do inspectors inspect the right things and do they come to accurate judgements?
“Ofsted produces an enormous ‘backwash’ in England’s schools. The consequences of a poor inspection judgement provoke fear amongst school leaders and an epidemic of over work in the profession which is driving teachers and school leaders away from teaching.
“We have to question whether Ofsted is a catalyst for improved educational performance in our schools.”