Primary school teachers have been allowing children to change gender without informing their parents, against government advice, according to the largest survey conducted so far.

An examination of over 600 school equality and transgender policies indicates that as many as three-quarters are currently misinterpreting laws around sex and gender. Some schools have implemented policies allowing boys who identify as girls to use girls' facilities such as toilets and changing rooms.

One educational trust, which advises several Church of England primary schools, has advised teachers to support girls using breast binders during school trips and to allocate sleeping arrangements based on students' self-identified "gender identity".

These policies persist despite the publication of government guidance in December, which asserts that schools should not automatically accept requests for social transition and should involve parents in any decisions made.

Gillian Keegan, the Education Secretary has previously said, “parents should not be excluded from decisions taken by a school or college relating to requests for a child to ‘socially transition’”, and has warned teachers that requests from students to transition their gender should be approached cautiously.

However, an analysis conducted across Devon and Cornwall reveals that 73% and 62% of schools respectively are misrepresenting equality laws. The findings, compiled by Protect and Teach, a network of concerned women, were prompted by the regions' high rates of referrals to gender identity services.

The findings, published by the Telegraph yesterday, come shortly before the anticipated release of the Cass review, which will evaluate gender identity services for children and acknowledge the role of schools. The first part of the review warned that social transition, as being practised here, is “not a neutral act.”

Common errors in school policies surrounded the confusion of “sex” (as defined by biology) with “gender” (that is, someone’s inner sense of self). A leading grammar school, for instance, defined sex as “a person’s understanding and experience of their own gender identity”.

Biological sex is protected in law by the Equality Act, whereas gender identity is not, and confusion around what sex actually is jeopardises single-sex sports and single-sex spaces.

Other policies suggested that children as young as five can display signs of gender dysphoria.

Concerns had already been voiced that the Government guidance would be ignored by schools, with some unions advising teachers that it was not ‘legally binding’.

The Conservative MP Miriam Cates, who herself used to be a teacher, responded:

“This research is highly concerning as it shows that a significant proportion of schools still have policies that are consistent with neither the law nor safeguarding.

“To keep children safe, adults must always know and be truthful about whether a child is male or female and any policy that allows or encourages teachers to ‘transition’ children is clearly wrong.”

A spokesman for the Department of Education also commented:

“We are absolutely clear about the importance of biological sex, particularly in the context of safeguarding, and the role parents must play in decisions about their children.

“Schools and colleges are expected to follow all guidance issued by the Government, whether it is statutory or not.

“Our guidance is clear that in nearly every case schools should not support the social transition of primary aged children, including not using pronouns that do not align with the child’s sex.”