Too many schools are taking an "oddly piecemeal" approach to teaching British values, Ofsted's chief inspector has warned.
British values such as tolerance and democracy should not be taken for granted, Amanda Spielman has said.
Ms Spielman made her comments today as she set out the role of teaching and a strong curriculum to promote British values in schools and prepare young people for life in modern Britain.
She warned that there is always a risk that "disenchantment" with life can be exploited by extremists who "promise a better tomorrow by scapegoating and blaming minorities today".
In a speech to the Policy Exchange, Ms Spielman recognised that schools can face challenges in teaching British values – for example, they may be teaching messages that are at odds with those youngsters hear at home.
But she raised concerns that often, these values are being taught in a way that "too seldom builds the teaching into a strong context".
She said: "When it comes to British values, we often see an oddly piecemeal approach, which too seldom builds the teaching into a strong context.
"One strange example I saw that illustrates the tendency to superficiality was in a prison classroom. The lesson was on writing a business plan: perfectly sensible stuff about setting out clearly the business idea, who the customers were, how it was going to be sold, how it would be priced, and so on.
"And then the teacher said ‘and of course you have to make sure that the plan reflects British values’ and started asking students how they would build each value into their plan."
She gave another example based on a visit to a secular school. The school had explained that one of the ways they teach fundamental British values is by looking at the seasons and weather "which is surely stretching the definition a bit", according to Ms Spielman.
She said: "More generally, we see a lot of wall displays and motivational assemblies, but not much coherent thinking about how a real depth of understanding can be built through the academic curriculum...Though, as ever, there are some excellent counter-examples."
She stressed the need for a strong academic curriculum that covers these core principles to help pupils identify "fake news and siren voices".
Ms Spielman told the think tank that only a small number of countries fully embrace what is known in the UK as British values – democracy, tolerance, respect and the rule of law – and that this "should be proof enough that we cannot simply take them for granted".
She suggested there is more that schools can do to teach these values within subjects such as history, geography and religious education (RE).
The curriculum is "vitally important in preparing young people for life in modern Britain", she said.
She added: "It gives young people an understanding of the forces that have shaped and continue to shape their history and nation. It helps them be discriminating about fake news and siren voices."
She went on to say: "Schools with the job of promoting British values and equalities are sometimes teaching young people who get conflicting or even downright contradictory messages outside school.
"For example, freedom of belief is inimical to the prevailing view in some communities. Similarly, the acceptance of the equal rights of women or of gay rights may not fit with the views a child hears at home. No wonder, therefore, that some young people feel torn between different identities."
Another issue is that "history, culture and experience can lead to a strong identification by a child with their family's cultural group to the exclusion of all else," she said, while a "practical difficulty" for schools is that education "rightly is seen neither by policymakers nor by teachers as indoctrination".
"Education should not and does not aim to force children to adhere to British values and to disclaim all others. Nor does it try to turn children against their parents or their cultural heritage."
She told Policy Exchange that it was important that issues such as British values are discussed.
One survey has suggested that just 25 per cent of those born in the 1980s think it is essential to live in a democracy, she said, compared with 70 per cent of those born in the 1930s.
Ms Spielman said: "For many people, the things I have been talking about today are too sensitive and too difficult for them to want to risk giving offence. They are easy things to skirt, yet the risk of doing so is great.
"If we leave these topics to the likes of the EDL and BNP on the one hand and Islamists on the other, then the mission of integration will fail.”