Segregation of teachers and other staff by gender is still being imposed at some independent faith schools, the chief inspector of schools Sir Michael Wilshaw has warned.
In a letter to the education secretary he said training for male staff at a school in Luton took place in one room and was broadcast to women in a separate part of building.
In another incident the school segregated male and female staff using a dividing screen across the middle of the room during an initial meeting with inspectors from Ofsted.
Mr Wilshaw said the meeting was not carried out in a religious setting but in a classroom, warning that such segregation flouts the requirement to promote 'fundamental British values' in schools.
He first wrote to education secretary Nicky Morgan about segregation of staff and governors at independent faith schools in November, but emergency follow-up inspections of three independent faith schools earlier this month showed that the practice was still going on.
He urged Ms Morgan to review the Department for Education guidance introduced in 2014 and, if necessary, write to independent faith schools to clarify government expectations and commitment to the promotion of 'British values'.
'This sort of behaviour manifested by the leaders of this school clearly does not conform to the spirit of the equalities legislation which underpins the spiritual, moral, social and cultural standard,' he said.
'Any form of segregation, without a good educational reason, is likely to lead to an inadequate inspection judgment for leadership and management.'