Schools in England must promote respect and tolerance in pupils for all faiths, races and cultures, says new government guidance on British values.
The guidance follows calls by ministers for schools to actively promote British values after concerns about an Islamist takeover in some Birmingham schools.
The advice is aimed at head teachers and governors at maintained schools.
Most "will find they have been actively promoting British values for years", said heads' leader Russell Hobby.
The push for schools to boost British values was among a series of proposals in the wake of the so called Trojan Horse allegations about a group of schools in Birmingham.
An anonymous letter claimed hard-line Muslims had been trying to impose their views on the schools, taking over governing bodies and marginalising head teachers.
Following investigations by Ofsted, five schools were placed in special measures.
In June, the then education secretary Michael Gove, said pupils must be made aware of fundamental British values of democracy, the rule of law, individual liberty, mutual respect and tolerance of different beliefs.
His views were backed by the Prime Minister.
Publishing the advice, the Department for Education, said the requirement for schools to promote British values is already set out in the 2002 Education Act.
A DfE spokeswoman said the guidance was intended to make clear to schools the extent of their duties under the Act.
In particular, the guidance emphasises that pupils should be encouraged to understand that "while different people may hold different views about what is right and wrong, all people living in England are subject to its law".
Schools' ethos and teaching "should support the rule of English civil and criminal law and schools should not teach anything that undermines it".
The guidance urges schools to take particular care to ensure pupils understand the difference between the law of the land and religious law.
They should "challenge" opinions or behaviour in school that is contrary to fundamental British values, it adds.
The guidance says schools must meet requirements for a daily act of collective worship, but they should also ensure pupils understand that freedom to choose and hold other faiths and beliefs is protected in law. Having another faith should not be the cause of prejudicial or discriminatory behaviour, it explains.
Pupils should also learn how citizens can influence decision making though the democratic process and how power in Britain is separated between the executive (government) and the judiciary.
The document suggests various classroom and extra-curricular activities to promote British values. It gives examples such as setting up a school council or using general elections to run mock votes and debates so pupils can argue and defend points of view.
Mr Hobby, general secretary of the National Association of Head Teachers, said the majority of schools were already meeting these requirements.
"Every school council, all of their personal social and health education, their behaviour policy, their broad approach to religious education - all exemplify British values.
"Our advice for most members is: don't do anything new, make sure you capture and describe the good work you are already doing."
The Association of School and College Leaders welcomed the guidance but warned that the area was complex.
"We cannot approach this task through a single lens," said the union's director of policy, Leora Cruddas.