The question of what schools should be doing to build a more cohesive society has returned with force. Recently we have heard the prime minister criticising the "doctrine of state multiculturalism" and calling for "a clear sense of shared national identity". The need for debate on these subjects has been underlined by the inquiry into the 77 bombings, which has received evidence about the work of the attack's ringleader in a Leeds primary school.
Yet the duty on schools to promote community cohesion has effectively been watered down since the autumn. The education secretary has removed Ofsted's responsibility for checking it, saying that it was "peripheral". Others had accused it of sidetracking teachers from their core mission and argued that measuring the impact of schools on their communities was impossible.
Clearly schools should not be subject to passing political fads, and many would agree that the inspection regime had become over-complicated. There should also always be debates about what schools are for.
But because the duty to promote community cohesion was inspected it was, therefore, important to headteachers and, as a result, began to create a wider network of successful practice. A concern must be that if this work is now seen as peripheral, will schools have the impetus to take it forward?
I became more involved in this topic after I was asked in 2006 by the then education secretary to be lead writer on a report titled Diversity and Citizenship in the Curriculum.
Launched the following year, the report seemed to be part of a response to a world that had been shaped by 911 and 77. The fear of terrorism, and the concerns of the then chairman of the Commission for Racial Equality that the country was "sleepwalking to segregation" created a bubble of interest in how to tackle these issues in local authorities and schools.
We were asked to review two things: first, the teaching of ethnic, religious and cultural diversity; and second, whether modern British social and cultural history should be a pillar of the citizenship curriculum.
Our conclusion was that those two topics should be tackled in tandem. Through their school experience and the curriculum, all young people should be able to feel that the ethnic, religious and cultural aspects of their identity are recognised and understood.
When we spoke to teachers and other stakeholders, there was interest in national identity and the idea of Britishness.
The concept of a national identity is harder to pin down today than in the days when Britain saw itself as essentially white and Christian. However, our response was that a notion of national identity does exist. It is complex, and has become more so as Britain has become more diverse. We felt it should be the subject of debate in schools.
A project that came out of our report was Who Do We Think We Are week, which involved thousands of schools until funding was stopped after the last election. The themes for the week went beyond subject, boundaries, as pupils explored subjects including belonging, faith and Britishness.
The project involved the Schools Linking Network, which held events across the country to bring young people from different schools together. The network, now a national organisation, started in Bradford at the time of the inter-ethnic disturbances in northern cities in 2001.
When we had visited it we were impressed by its work linking Year 5s from a largely white school to those from a predominantly Asian school. One white boy said how he had enjoyed a visit to a mosque because his new Asian friend had talked to him about it and made it seem more everyday.
While I would not claim our report, or the duty, have transformed relationships for young people, they have kick-started pieces of work that have led to further debate.
There is more work to do in the curriculum around religion. At the heart of the prime minister's speech was a concern with Islam and the relationship between religion and extremism. Yet where in the citizenship curriculum is work done to understand what belief means and the relationship between religion and politics? Writing the report in 2006, our sense was that many schools were silent about 77 because it was beyond their capacity to discuss it. We might have moved on, but there are still roads to travel.
What about how we discuss race - a potential fault line in our society? There are questions to be discussed in schools about why race leads to inequality and how the media shapes views.
Similarly, social class divides us. The English Defence League and the BNP are seen as white working-class movements representing those who feel dispossessed in their own country. However, in polite society, it seems more acceptable to use a word like "chav" than a word like "Paki", though both are discriminatory.
If white students feel isolated, community cohesion will not happen. An Ipsos Mori poll for the education charity Think Global indicates that only 47 per cent of white students think it is a good idea to have people of different backgrounds living in the same country together.
Recently the work on community cohesion has been confused by aspects of the "Prevent Agenda" against terrorism. A rethink is needed on how that plays out in school.
When it comes to community cohesion, my argument is that a body of work is developing, that it is important, and that it needs support and direction. The official duty to promote it may fade, but I believe that in the 21st century it must be a moral imperative for those working with young people. Unfortunately schools are not as accountable for moral imperatives as they are for legal duties.
Sir Keith Ajegbo is a former head and led the report on Diversity and Citizenship in the Curriculum.