Nigel Williams signals his difference from other adults when - in front of an assembly at Limavady Central primary school, County Londonderry - he starts barking like a dog, while explaining the role of a children’s commissioner.

Once the barking has broken the ice, the “watchdog”, whose job is looking after children’s interests in Northern Ireland, asks a question that prompts urgent, incredulous, whispering. “Is there any way you’d like to change your school?” The conferring blonde, brown and ginger heads at first hardly dare to reply, but once they get going there is no stopping them.

Why can’t they have a vending machine? More to do in the playground? Why can’t girls play football, and why do teachers have nice chairs when children don’t? By the end of the assembly they are questioning why they have to go to school at all, and why teachers get paid when “we do all the work”.

Children appear to enjoy the visit from the Children’s Commissioner for Northern Ireland more than some teachers do. As one staff member observes grimly at the end of the assembly: “It’s nice for them to be heard.”

On a range of issues, it is the children’s right to be heard. Britain (along with every other country apart from Somalia and the United States) has ratified the United Nations Convention on the Rights of the Child (UNCRC) - although a UN monitoring body recently found that British children’s rights were being breached in several areas, some relating to education. Campaigners (including Prime Minister’s wife Cherie Booth QC) have been calling for a children’s commissioner for the UK for more than a decade to ensure the principles of the convention are respected. Instead, separate commissioners have been established, and now, following Wales, Northern Ireland and, most recently, Scotland, England is to have its own children’s champion, with legislation outlined in the Children Bill published earlier this month. Children’s rights campaigner Esther Rantzen is among those touting for the job. But activists are angry that the plans do not go far enough, allowing the English commissioner to carry out formal investigations only at the direction of government ministers, in contrast to the other three commissioners.

Each commissioner, within the constraints of his or her legislation and budget, has first to create an administrative and ideological structure for the post. After 15 years living in London, where he was a Liberal Democrat councillor in Southwark and founded a charity to protect children on the internet, 49-year-old former civil servant Mr Williams has returned home to Northern Ireland to do the job. With an annual budget of pound;1.9m and strong powers, he is establishing offices in central Belfast in a non-sectarian area close to transport links.

Mr Williams, who took up his post six months ago, identifies a range of issues facing Northern Ireland’s children. The “bright spots are brighter” than in England, he says, with some experiments involving children in decision-making. “But the dark spots are darker.”

Chief among these is the influence of paramilitaries in some urban communities, blamed for a spate of child suicides in north Belfast over the past year. Pockets of extreme poverty are another concern, and a society where “conservatism is mixed with sectarianism” can be inimical to children’s rights. The recent decision to abolish the 11-plus and selective schools by 2008 is a move forward, he says.

Part spokesperson, part ombudsman, part lobbyist, a children’s commissioner must have the humility to listen to children, and the independence of mind to stand up to the government of the day when necessary - while simultaneously influencing policy-making. Mr Williams, whose legislation clearly expresses the necessity of involving children in his work, is embarking on a series of informal consultations with children, many of them in schools like his own alma mater, Limavady Central. “I was here shortly before the dinosaurs,” he tells the assembled children.

But crowd-pleasing apart, the commissioner has the right to investigate services, initiate reviews and take legal action - alongside the general duty to promote children’s rights. The push towards integrated services is complex in Northern Ireland, where health and education come through four education and library boards and five health trusts. The barriers to joint working are considerable, but Mr Williams stresses that “if you want people to change, you have to take them with you. It’s not about walking in with jackboots on.”

There is a debate about how useful it is for commissioners to respond to individual complaints from children or parents; neither Kathleen Marshall in Scotland nor the English commissioner will deal with casework. But Mr Williams believes casework “increases your contact with real people’s lives”, and has set up a division in his office to field calls. Staff usually refer children or adults to the relevant bodies, but will take up a cause if necessary.

Last year, the commissioner’s office was approached by a single mother with three children including a terminally ill child who used a wheelchair. The housing authorities had agreed to adapt their home - but local paramilitaries intimidated the builders off-site. Mr Williams led a meeting of interested parties in the community, and the issue was resolved. The case shows the scope of the commissioner’s role - from macro to micro. Mr Williams is keeping the bigger picture in mind and says he hopes to be a catalyst for children’s interests in Northern Ireland.

Fifty-five-year-old Peter Clarke, Children’s Commissioner for Wales for the past three years, seems to have had an impact on children’s rights, after a difficult first year setting up administrative structures and premises. He has successfully pressed for 11 to 18-year-olds’ right to challenge school exclusions, and has made school toilets the subject of a debate in the Welsh Assembly. He has also initiated a public inquiry into the case of John Owen, a Welsh teacher who killed himself in 1991 following allegations of child abuse.

It is difficult for adults in middle age to claim they represent children.

Mr Clarke’s office solicits children’s views via an email club and school visits; staff are continuing to build networks for consultation. The issue, says Mr Clarke, is getting a sufficient number and variety of groups of children to make what he says meaningful to them. “My dream is that before I leave, if there is a major issue, we’ll be able to garner the views of thousands of Welsh children before I open my mouth.”

Commissioners in Britain, as under the UNCRC, have particular responsibilities to look out for the interests of vulnerable children, such as those in care, with disabilities, or from ethnic minorities, and young carers.

Despite a supportive political context - the Welsh Assembly is broadly behind young peoples’ involvement in decision making, and Wales has a youth parliament called the Funky Dragon - Peter Clarke finds a prevailing message from children in Wales that they feel “disrespected, generally” by adults. And bullying is a perennial concern of children. The Welsh commissioner’s powers are limited to those areas devolved to the Welsh Assembly - excluding important areas such as youth justice - and this is a frustration.

With children’s rights rising up the political agenda, schools are likely to be a testing ground. “It will be played out there; I’m making every effort to make sure it isn’t fought out,” says Mr Clarke. He says that whereas relationships in the domestic sphere have moved on from a Victorian authoritative model, to be more about negotiation, the same has not occurred in schools. “Schools have yet to evolve adequate means for negotiating with children. It is still an archaic structure.” While some aspects of school life are “non-negotiable”, he says children could be involved in a spectrum of decision making covering uniforms, rules and punishments.

Elsewhere in Europe, children’s commissioners or “ombudsmen” are part of the political landscape, with some 25 in post. The idea of commissioners, says Trond Waage - children’s ombudsman in Norway since 1996 - is “emblematic of a modern society”. Mr Waage has been an outspoken champion of children but kept channels open with ministers - the secret of success, says children’s rights campaigner Peter Newell, secretary of the European Network of Ombudspersons - and has persuaded Norway’s government to outlaw bullying, adopting a zero-tolerance policy, and holding administrators responsible for the situation in their schools.

Norwegian children learn about the ombudsman’s office at school, and Mr Waage is concerned with childhood in the round. “We look at the impact of divorce, education, public care, cosmetic surgery. We are monitoring the shadow side of society, through childhood.”

Mr Waage, who exits his post next month, wants legislation to protect children from passive smoking in the home, more honest debate about divorce and changing family structures, and a change in the perspective that sees children as the property of their parents. “Children are a community responsibility. We have to move the goalposts so adults see children as subjects, with rights.”

While legislation to strengthen children’s individual rights is useful, he warns against a possible latent effect - that the community may cease to feel any joint responsibility for its young, instead delegating all to statutory systems. “You could lose social codes, empathy, the glue of democracy,” he says.

For information on children’s rights in England visit www.crights.org.uk.For more details of European Ombudspeople, visit www.ombudsnet.org