Schools' curriculum 'should be rated separately'
Heads are calling for schools to be graded separately by Ofsted on the breadth and balance of what they teach.
National Association of Head Teachers leader Russell Hobby says too often "specific ideological agendas" have led to a narrowing of the curriculum.
A number of schools were downgraded recently due to a too narrow curriculum. This is evaluated as part of the Ofsted category of school leadership and management.
Ofsted is to respond in due course.
It has just closed its consultation on a new inspection framework, which will introduce shorter inspections for all schools rated good in England.
But Mr Hobby said in his submission to the consultation that a separate grading on the curriculum itself would encourage more of a focus on what is taught in schools.
He argued it could ensure pupils received all their entitlements to subjects, including music, sport and sex and relationship education.
This issue was highlighted in the wake of the "Trojan Horse" affair, where a Muslim-dominated governing body tried to influence the ethos of several schools.
And a series of snap inspections, some on faith schools, found there was a lack of breadth in what was being taught in some schools - particularly in religious education.
Ofsted chief inspector Sir Michael Wilshaw has highlighted his concerns, particularly in relation to the narrowness of the curriculum in a number of schools, in a letter to the Education Secretary, Nicky Morgan.
Mr Hobby said: "All children are entitled to access a broad and balanced curriculum. Too often, however, external accountability drivers and/or specific ideological agendas have resulted in a narrowing of the school curriculum.
"In some cases this has resulted in children missing opportunities to engage in sports, the arts or other enriching activities.
"We want Ofsted to tell us things that we can't see about schools. If all Ofsted do is look at the exam data, then it's not really doing that," he added.
Mr Hobby also pointed out that this "is a time of enormous upheaval in terms of curriculum and assessment, with significant change occurring in every sector".
A new national curriculum has just been introduced to primary schools. This involves significant changes to maths, history and English teaching, among other subjects. And changes to GCSEs are being phased in over a number of years.
An Ofsted official said it was grateful to the NAHT for providing its views and thanked the association for its support during the consultation process.
"We will be considering their response carefully, along with all other responses received, once the consultation has come to a close."
A spokeswoman for the Association of School and College Leaders said it did not support the proposal for the curriculum to be graded separately.
"A separate grade for curriculum could imply compliance with a set view of an imposed curriculum which may not be in the best interests of individual students.
"Judging the curriculum as part of leadership and management ensures it is for senior professionals and governors to determine the curriculum for their students within the context of statutory requirements."