Students attending a school managed by Park View Educational Trust in Birmingham had "scant" understanding of non-Muslim faiths, as the religious education curriculum focused primarily on the study of Islam, ITV News understands.
Other criticisms of the school, included in a Ofsted report due to be released next week, said female members of staff at the school were left feeling "intimidated."
The inspectors are expected to recommend that students and staff understand the risks associated with extremist views.
The leaking, from her department, of a letter to Michael Gove, raises serious questions for the Home Secretary to answer.
One school was praised by Ofsted for using money from the pupil premium to pay for a number of cultural trips to Saudi Arabia.
Six Birmingham schools will be rated 'inadequate' and several more downgraded. Council officials have been criticised for failing to act.