Schools are being told they have a "fantastic opportunity" to tackle inequality between the sexes.
Schools are warned not to tackle one problem and cause another
The Gender Equality Duty, which came into effect this month, applies to all public bodies - of which the biggest single group is schools.
Head teachers and governors in England have now been sent 40 pages of guidance by the Equal Opportunities Commission.
"Key issues" include stereotyping in subject choices, boys' poor attainment, girls' lack of exercise, and bullying.
Schools have until the end of the month to devise an action plan.
Governors are reminded that the legal responsibility for implementing the gender equality duty rests with them.
Staff are encouraged to read the guidance, and it should be "shared with" pupils, parents and other carers.
"The gender equality duty presents a fantastic opportunity for schools to make a co-ordinated effort to tackle inequality and ensure that all pupils are able to fully achieve their potential," the commission says.
"This should act as a catalyst towards a society where we all can make the best of our life chances."
Gender impact assessments will need to be drawn up for areas such as the curriculum; uniform; objectives to do with being healthy, enjoying and achieving; admissions; discipline; sports and careers and work experience.
The president of the Association of School and College Leaders, Malcolm Trobe, said schools needed information that was clear and concise.
Needlessly long documents were not only off-putting, they made it difficult to take everything into account when determining a school's policy and practices.
"We need to have laid out more clearly exactly what is regulatory or in statute and what is simply guidance.
"Guidance should be what it says - guidance - and guidance doesn't always have to be followed."
Nursery and primary schools look to have a problem with staffing - only about 16% of their teachers being men. In secondary schools it is 44%.
A blog which highlights male gender discrimination, The Rights of Man, draws attention to the under-performance of boys as "a serious area of concern".
In last year's GCSE results, 41.5% of boys attained the equivalent of five good grades including English and maths compared with 50.2% of girls.
But schools need to be careful if, for example, they introduce "catch-up" classes for boys, the guidance says.
"This approach is likely to be unlawful, unless similar assistance is provided for underperforming girls."
Girls' educational achievements are not necessarily helping them into well-paid jobs.
"Eliminating gender stereotyping in school education, in vocational training, and in careers choices is a vital step towards tackling the gender pay gap in employment," the guidance says.
Girls are felt to be in need of more attention where exercise and obesity are concerned.
Girls aged seven to 11 are less than half as likely as boys to take part in PE and sport.
By the age of 18, 40% of girls have dropped out of physical recreation
Five schools in Norfolk have decided to tackle this problem by employing a "well-being mentor" whose role will be to stop teenage girls from becoming "disengaged with PE and sport".
The mentor will be based at Rosemary Musker High School, Thetford, and also work in four nearby schools.
The post, thought to be the first of its kind in Britain, is being funded by lottery cash.