Government guidance on the new Relationships and Sex Education (RSE) curriculum has been hailed as a "victory for safeguarding and common sense" by critics.
The guidance, from the Department for Education (Df), warns schools against promoting transgender ideology among students or using resources that have been produced by organisations "that take extreme political stances on matters".
Examples of extreme political stances given in the guidance include those in "opposition to the right of freedom of speech, freedom of association, freedom of assembly or freedom of religion and conscience".
The guidance states that pupils "should leave school with a proper understanding of the importance of equality and respecting and understanding differences", including "differences in religion, belief, or sexual orientation".
Importantly, it tells schools that resources around gender and sex must be evidence-based.
"We are aware that topics involving gender and biological sex can be complex and sensitive matters to navigate. You should not reinforce harmful stereotypes, for instance by suggesting that children might be a different gender based on their personality and interests or the clothes they prefer to wear," it reads.
"Resources used in teaching about this topic must always be age-appropriate and evidence based. Materials which suggest that non-conformity to gender stereotypes should be seen as synonymous with having a different gender identity should not be used and you should not work with external agencies or organisations that produce such material.
"While teachers should not suggest to a child that their non-compliance with gender stereotypes means that either their personality or their body is wrong and in need of changing, teachers should always seek to treat individual students with sympathy and support."
It adds that schools should "work together with parents on any decisions regarding your school's treatment of their child, in line with the school's safeguarding policy and the statutory guidance on working together to safeguard children."
Elsewhere, it says that RSE lessons should be "age appropriate" and "careful not to expose children to over-sexualised content", while local authorities and schools are told they must ensure a "balanced presentation of opposing views".
The Values Foundation, which is meeting with the DfE next week about an independent RSE watchdog, welcomed the guidance, calling it "a victory for safeguarding and common sense".
"It's now more necessary than ever to ensure that schools stay within the implementation guidance," the foundation said.
The Christian Legal Centre's Roger Kiska has also welcomed the guidance while also urging parents to "stay vigilant" about what their children are being taught in schools.
"With the exponential increase in children being referred to gender identity clinics each year (an increase of over 2500% over the last decade), the DfE has now signalled the alarm bells that this type of teaching and the external agencies which promote them have no place in our schools," he said.
Mr Kiska said he hoped the new guidance would usher in a time of "healing" from harmful ideology.
"While this is likely not the end of partisan campaigning groups trying to win the hearts and minds of our children over to their ideological and political persuasion, this is nonetheless a huge leap forward for parental rights and keeping our children safe," he said.
"It means most likely that radical groups like Mermaids, which have in such a short time wreaked utter havoc among our young people, will finally be side-lined.
"It means – I hope and pray – that a period of healing can begin where we allow our children to be children, not objects to be won over to harmful new ideologies."
Catholic journalist Caroline Farrow welcomed the guidance in a Twitter thread in which she strongly criticised the Catholic Church.
"At times I felt like I was the only Catholic voice speaking out about what was going on in our schools and resisting gender ideology, with no back up or support from the institutional Church, who was still smarting over gay marriage & wary of getting her fingers burned," she wrote.
"Now that the DfE have issued this revised guidance there really is no excuse for the CES and Catholic schools not to stand up to Stonewall et al instead of capitulating.
"It's been a really positive week for women in the culture war, with the GRA reform largely abolished & now this DfE RSE guidance. But from a Catholic faith perspective, it's clear the hierarchy want the laity to do the heavy lifting."
Where was the Catholic Church & Catholic Education Service in this fight to get gender ideology in schools? Oh yes, that’s right, inviting Stonewall in to write policy & copying secular schools ‘best practice’ of letting students choose which toilets to use.— Caroline Farrow (@CF_Farrow) September 24, 2020