Ofsted is giving its inspectors extra help because of concerns about their reliability in checking the secondary curriculum under the watchdog’s new inspection framework, it was revealed this morning.

Research by the watchdog has found that using workbook scrutiny and lesson visits to assess teaching quality and curriculum was less effective in secondary school than it was in primary schools.

Daniel Muijs, Ofsted’s deputy director for research and evaluation, said this was because inspectors were “looking at lessons outside of their subject expertise.”

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To counter this issue, he said, Ofsted was giving its inspectors “subject-specific guidance” in all subjects to improve the reliability of their inspections.

The findings come in a report the inspectorate published today, which highlights how it will look at lessons and pupils’ workbooks as part of the deep-dives in specific subjects it will complete to assess a school’s curriculum under the new inspection framework.

The research explores the reliability of these methods of assessing teaching, curriculum and behaviour by using paired assessments.

Professor Muijs said: “In schools, we found substantial levels of reliability in primary and on behaviour in secondary. We found only good levels of reliability on curriculum and teaching in secondary.

“That the secondary curriculum and teaching measures were lower was due to inspectors looking at lessons outside of their subject expertise. To counter this, we are developing subject-specific guidance for inspectors in all subjects. This is in collaboration with expert groups.

“Overall, though, within a high-inference (subjective) model that requires a lot of observer judgement, this is a positive outcome.”

The research scrutinised more than 300 workbooks from years 3, 4, 5, 8 and 9, covering maths, English, history and geography, science and French. 

Ofsted said nine HMIs independently looked at the work, with two scrutinising each book to allow Ofsted to assess the reliability of this approach.

Curriculum is a major focus of the new inspection framework being introduced in September. Inspectors will look at the intent, implementation and impact of the curriculum as part of a new quality of education judgement.