It's a reasonable question to ask. Inspectors are highly accountable. Every report goes through at least two independent quality checks to ensure that it is consistent, explains convincingly what is working well and what less well and that it complies with Ofsted's reporting requirements.
Inspectors' evidence is routinely checked by another experienced inspector unconnected with the inspection. Such checks confirm whether the inspection findings are based in recorded evidence. In turn, all inspection reports are signed off by a Her Majesty's Inspector (HMI).
The evidence base is independently checked whenever an inspection determines that a school should be put into special measures or issued with a notice to improve. Furthermore, all reports that judge a school to require special measures are signed off by Her Majesty's Chief Inspector.
Inspections are also monitored as part of the quality assurance processes of the regional inspection service providers with whom Ofsted contracts for organising inspections, and by HMI employed directly by Ofsted.
I have been asked to visit an inspection to check that it is being properly conducted, and have had HMI monitor my own inspections. Such on- site monitoring will involve discussion with the headteacher as well as checking the evidence being collected. It may involve sitting in on meetings with staff and pupils or on the end-of-inspection feedback.
On every inspection, there is an opportunity for the school to say how the inspection has been conducted and on whether it has been helpful via a post-inspection survey or through the quality assurance visit itself. Ofsted also calls in the full evidence base for many inspections, partly to help with research purposes and also to ensure inspectors are kept up- to-date and effective in their own practices.
In addition to routine checks, there will always be a check made in the event of any complaint lodged after the inspection. Again, this will involve a rigorous examination of the inspectors' recorded evidence.
Selwyn Ward has been an inspector for 15 years, working in primary and secondary schools. The views expressed here are his own. To ask him a question, email him at email@example.com.