School leaders will be used to being asked: “How do you know?” But this time around, it’s Ofsted facing the tricky questions. Do we understand well enough the footprint that inspection leaves behind, particularly in the most disadvantaged communities, and can Ofsted provide evidence of its positive impact on those schools?

A recent blog post by Stephen Tierney, using Ofsted’s own data, has prompted discussion about the extent to which the inspection system is stacked against schools with higher levels of disadvantaged pupils, particularly in secondary school. In fact, the realisation that inspection tends to favour less-disadvantaged cohorts is not a new one. In 2016, the Education Policy Institute found that “there is a clear and systematic negative correlation between school intakes with more disadvantaged children and more favourable Ofsted judgements.”

Some commentators have taken to Twitter to argue the latest evidence shows an institutional bias against schools with high proportions of disadvantaged white British pupils. It’s unsurprising that Ofsted has strongly refuted this, and a follow-up blog from Jason Bradbury, deputy director for data and insight, and Sean Harford, national director for education, provided amended graphs and explanation to support interpretation of the data.

But what are the reasons for the lower Ofsted grades given to these schools? The view from Ofsted is that judgements merely reflect the quality of education in these schools, and are born out of the challenges schools in these areas face. “Only this week,” Sean Harford explains, “two separate reports show that not only are schools in deprived areas more likely to employ less experienced teachers, but also those with lower levels of subject qualification.

“Similarly, the recruitment of leaders and managers is more difficult in these areas. And this includes recruiting effective governors, which is particularly difficult when the communities are disaffected, monocultural and lack capacity.”

In just three sentences we are given half a dozen reasons why educational inequality continues to persist in this country, but arguably one of the most important factors is not addressed - the role of inspection itself.

Ofsted is committed to being a ‘force for improvement’, and few would argue with this ambition. But, what if in trying to do so it actually caused harm to the very communities that needed the most help? Would this be serving schools, would it be serving parents and taxpayers, and would it be serving pupils?

There is anecdotal evidence that adverse inspection judgements contribute to the sort of capacity issues Ofsted itself identifies as limiting the quality of education, but Ofsted hasn’t got to grips with this issue yet. This is despite its 2017-22 strategy stating: “We should ensure that our judgements and grade profiles are fair and not barriers that deter talented professionals from working in areas where young people are most in need of support.”

Arguing that inspection is fair in terms of consistency and reliability is one thing, but exploring its impact on schools, pupils and communities is altogether different and needs to be addressed urgently - for the inspectorate’s sake as much as anything.

A recent investigation by the National Audit Office into Ofsted’s value for money was not particularly conclusive, although it did state that: “Ofsted does not know whether its school inspections are having the intended impact: to raise the standards of education and improve the quality of children’s and young people’s lives.”

The reality is that we don’t know well enough the footprint that Ofsted leaves behind, including in areas of deprivation. Is Ofsted helping or hindering those schools and communities which find themselves statistically more likely to be on the wrong side of an Ofsted judgement?

It was psychologist Samuel Messick who coined the phrase ‘consequential validity’ when exploring the potential negative consequences of an otherwise valid test. He made the point that tests which are technically valid can yield negative social consequences which, in turn, undermine the intended effect of the test. Might the same be true of inspection?

Ofsted needs to return to the promise of its 2017-22 corporate strategy and dig into the consequences of inspection, positive and negative. Until such time, it will remain vulnerable to the suggestion that it serves to entrench educational inequality rather than solve it.

Stephen Rollett is the inspections and accountability specialist at the Association of School and College Leaders.