School leaders are worried that the widespread practice of starting GCSE courses before Year 10 will be penalised by Ofsted under its new inspection plans.
Stephen Rollett, of the Association of School and College Leaders, told Tes that around half the union's members led schools running three-year GCSE programmes.
Chief Inspector Amanda Spielman has warned that shortening key stage 3 in order to allow more time for GCSEs can narrow the curriculum.
Mr Rollett, ASCL’s inspection and accountability specialist, said Ofsted’s view that a shortened key stage 3 could narrow the curriculum has caused concern for headteachers.
“When we survey our members, we have found it is about 50 per cent who offer a longer key stage 4," he said.
“I think, given that Ofsted has said that shortening key stage 3 can narrow the curriculum, there is a concern among school leaders with a three-year key stage 4 about how they will be looked at by inspectors under the new framework.
Ofsted's new approach
“I don’t expect that Ofsted would give an automatic negative judgement for schools with shortened key stage 3 and, given the number of schools who do this, I don’t think they could.”
However, he said that the number of schools running a longer key stage 4 could now drop because of fears about what Ofsted’s new inspection framework might mean for them.
“We think that it is right that Ofsted ask questions about the thinking that underpins a school’s decision on the curriculum," Mr Rollett said.
“What I think is critical is that schools are given time to develop their thinking on curriculum and that any changes they make are, firstly, their decision and, secondly, based on sound thinking and curriculum planning and not as a knee-jerk reaction of a school second-guessing what Ofsted wants to see.”
An Ofsted spokesperson said: "Ofsted does not intend to dictate the length of key stages in schools. Inspectors will be particularly alert, however, to signs of narrowing in the key stage 3 curriculums.
"If a school has shortened key stage 3, inspectors will look to see that the school has made provision to ensure that pupils still have the opportunity to study a broad range of subjects in Years 7 to 9.
"Our new framework will mean a renewed focus on the substance of education, and will bring the inspection conversation back to the curriculum – treating teachers as experts in their fields, rather than as data managers.
"School leaders and teachers should not make decisions about the curriculum based on a sense of what Ofsted wants to see.
"Rather, our new inspection framework will reward those schools that provide a broad and rich curriculum for their pupils at all of the key stages of primary and secondary school."
Ofsted published new research last week into how it intends to inspect the quality of school curriculum.
In its findings, it again raised concerns about key stage 3 narrowing and said that around half of the secondary schools it visited for curriculum research were running a three-year key stage 3.
Ofsted assessed the quality of curriculum of the schools it visited and placed them in five bands – with band five being highest.
Of the 31 secondary schools it assessed, three were placed in band two, 10 were in band three, 17 were in band four and one was in band five.
The research also showed that when judging individual secondary school departments, only one English department at a secondary school was rated poorly out of 16 and none of the 14 maths departments or eight science deparments that were assessed rated poorly.
In contrast, almost a quarter (six of the 26) humanities departments visited were rated in the bottom two bands. Next month the inspectorate will launch its consultation over the new inspection regime, which is expected to detail how its inspectors will assess curriculum.
Mr Rollett said: “There is tension in that Ofsted should not be so prescriptive that we have an Ofsted-prescribed approach to curriculum because that is not something that we would support – but it also must not be so vague so that it leaves school leaders not knowing what the rules of the game are.”