The new headline GCSE measure of student progression over attainment is a key reason why an Ipswich secondary school has lost its ‘good’ Ofsted rating.

St Alban’s Catholic High School in Digby Road was given a ‘requires improvement’ judgement after a two-day visit by six inspectors.

Broken down, behaviour was rated ‘good’ but leadership, teaching, pupil outcomes, and the sixth form require improvement.

It was the first inspection since the new Progress 8 accountability measure of student progression between the end of primary school and secondary school. Zero represents expected progress.

Provisional 2017 data shows St Alban’s scored -0.45, almost half a grade less per GCSE subject. But 66% achieved level 4 (old C grade) in English and maths, above the Suffolk and England averages.

Where does your school rank in provisional Progress 8 and GCSE results 2017 in Suffolk?

Lead inspector Russell Ayling wrote: “Attainment of pupils overall has been largely in line with national averages but this hides the fact that many pupils started their education at the school with above average prior attainment and have therefore not made such good progress.

“The school has been tracking how current most-able pupils are progressing and identified that some are not making as much progress as they had expected. Progress in English, mathematics and science is accelerating as the impact of improved teaching becomes apparent.”

The report said expectation levels for the most-able pupils are too low, some lessons plans do not take into account the needs of some groups, there is a lack of consistency in assessment between departments, and performance management “lacks precision”. But pupils show resilience during challenging work, personal development is outstanding, and new assessment systems have been introduced.

Executive headteacher, Sean Hayes, backed an action plan to turn around the rating.

He said: “We have noted the inspectors’ comments and accept the points that have been made about the need for pupils to make more progress. This aspect of our performance has affected the other judgements within the report and led to the overall judgement. We are pleased that the motivation and personal development of pupils was recognised. I am confident that we can see an improvement in our progress measure in 2018 and therefore quickly get back to where we should be.”