The Church of England says that at its schools, boys should be allowed to wear tiaras and tutus, in a policy it hopes will aim to curb transphobic bullying.
The church's instructions to the faith's 4,700 schools outline how children should not be required to wear uniforms that "create difficulty for trans pupils".
Male pupils should be able to wear a tutu or high heels without being commented upon, under the guidelines, which include tips for teachers to report bullies and their victims.
Teachers are also told to look out for trolling of pupils on social media, name-calling and gestures.
The C of E document, titled All God's Children, says children should be free to choose what they wear and that they "should be at liberty to explore the possibilities of who they might be without judgement or derision".
"For example, a child may choose the tutu, princess's tiara and heels and/or the fireman's helmet, tool belt and superhero cloak without expectation or comment."
The rules also describe how there will be school staff members in same-sex relationships, bisexual, trans or exploring their gender identity.
But Andrea Minichiello Williams of Christian Concern described the rules as "unkind, unloving and lacking in compassion".
"We are all against bullying, but the Church is using these guidelines to pursue an agenda that runs counter to the Church's teaching.
"We are getting to the point where if you are not careful the slightest slip from the correct agenda in a Church of England school will get you punished. The anti-bullying agenda is aimed against people who step out of line – the anti-bullies are becoming the bullies," she told the Daily Mail.
Barnardo's chief executive Javed Khan said: "Respecting the unique worth of every person is an integral part of Barnardo's values, so we wholeheartedly welcome this move by the Church of England."
A spokesman for Stonewall said: "We would like to congratulate the Church for sending a clear signal that homophobic, biphobic and transphobic bullying must never be tolerated," the Telegraph reported.
In 2014, the CoE published guidelines aimed at promoting greater harmony among people of different sexual orientations, saying that pupils "revere and respect all members of the diverse community".
Meanwhile, an adviser to the Archbishop of Canterbury, Lorna Ashworth, quit over her unhappiness at a "liberal" Church of England "agenda of revisionism". Ashworth, who opposes gay marriage, left the Archbishops' Council and General Synod what she described as an increasingly liberal direction taken by the church.