Lots of little boys like to try on the frilly dress and high heels in the classroom dressing-up box.
But for some the desire to identify with the opposite sex goes further than clothes. These children are "transgendered": they are convinced they have been born with the wrong sex.
Teachers who discover a transgendered pupil in their class are often uncertain where to get advice. One primary teacher turned to the TES online staffroom for help supporting a boy in her class who feels he is really a girl. "Diagnosis has been made, but not much support forthcoming," she said. "The parents are floundering. We want to teach our pupils to be accepting and tolerant of everyone, no matter how different they may be."
For many teachers, informal advice is all that is available. The Department for Education and Skills has no specific guidance yet the Department of Health maintains that transgendered pupils are the responsibility of the DfES.
The National Association for Special Educational Needs says it has never been asked to work with transgendered pupils. The Child and Adolescent Mental Health Services are wary of classing gender confusion as a mental-health issue, because it is not a condition that can be treated. The Anti-Bullying Alliance also has no specific policy to support transgendered pupils.
In a group of 100,000 people, about 1,000 will experience a degree of gender "variance". Around 25 will feel this acutely enough to want medical treatment. Of these, around three-quarters will be male-to-female.
Bernard Reed, of the Gender Identity Research and Education Society, said:
"It's part of nature's rich variety. Schools need to be aware of this and prepare teachers as they would for dyslexia. Unless it's handled carefully, it can lead to bullying and stress."
Gires produces a two-page factsheet for teachers to use with teenagers, outlining how physical gender can differ from gender identity, along with the options for transgendered people.
But classroom education on the subject is often controversial. Those with little knowledge of the condition mistake it for a sexual, rather than a gender issue.
One visitor to the TES online staffroom said: "I think this is social engineering of the worst kind. All kids experiment with their sexuality, but to make such an open invitation could just cause a hornets' nest of problems." Sue Sanders, of Schools Out, the lesbian, gay and transsexual teachers' organisation, said: "Schools had enough difficulty getting their heads round homophobia. Transphobia makes their eyes cross."
In fact, gender confusion can manifest itself in children as young as three, according to Mermaids, a gender-identity support group.
A spokeswoman said: "It's nothing to do with sexuality. It's what's between their ears, not between their legs. Their brains are programmed a certain way."
A number of children outgrow this confusion at puberty, and grow up as gay adults. Others remain transgendered. But Mermaids says forcing boys to play with toy trucks or girls with dolls will not alter their future.
A spokeswoman said: "The way you treat them isn't going to make a blind bit of difference to how they develop. They should be given loving support and acceptance, so they don't feel guilty."
TIPS FOR SCHOOLS
* Avoid separate boys' and girls' queues in the playground.
* Allow girls to wear trousers
* Provide a changing space for the transgendered child
* Put in a gender-neutral toilet
* Refuse to tolerate bullying and explain why
* Work with mental-health services, so all staff are aware of a transgendered child and their condition
* Ensure supply staff know who is transgendered
* Give all children support so they do not feel guilty about their identities