The nightmare of every school is a front-page tabloid headline screaming that their pupils were found accessing hardcore pornography in the classroom. And then there’s the concern that paedophiles might target school children via email and chat sites. Little wonder that a lot of effort has gone into developing filtering systems designed to stop children accessing violent, racist or pornographic material on the Internet.

Filtering is a controversial issue, not least because some people place too much faith in it, says Stephen Heppell of Anglia Polytechnic University’s Ultralab. “Some filtering system are just crude,” he believes. “For example, there are some schools that can’t access our sites because our address is in Essex and that contains ‘sex’. We have to show common sense when using the Internet, as we do in the real world. You don’t start talking to strangers at the bus stop, you don’t give anyone your home address and if someone is abusive, you don’t answer back. What’s far more important than a filtering system is a sensible schools’ policy so that students know what they can and cannot do.”

Adrian Carey, of educational Internet service provider (ISP) Edex, says:

“People expect perfect filtering systems and that’s illogical. Some systems analyse skin tones to block nude images. The problem is that they also stop you finding out about your local football team, and it overlooks the fact that kids can walk into any high street and see nude pictures on the top shelf.” Carey also feels uncomfortable about filtering children’s email:

“We don’t insist that we read every letter a child writes in school, so why do it with email?” But despite these reservations, few schools or educational ISPs would be happy to operate without some form of filtering system and few parents would like their children to have unfettered Internet access. Yet as the Internet grows, the task of filtering becomes more difficult. Tim Clark, of RM, which runs the Internet for Learning service, says his company’s filtering process will currently block over 100,000 websites and 10 million Internet addresses. “But we can’t be 100 per cent safe because it’s a moving target - new sites are always springing up and addresses can be easily changed,” he adds.

Early filtering systems were unsophisticated and simply blocked key words or phrases. Others blocked entire servers even if 99 per cent of the sites held on them were fine. The latest filtering software is more focused. Many use a system known as Dynamic Document Review (DDR), which analyses the contents of a web page and the context of the word combinations.

Jeff Joseph Sale Moor College in Manchester uses I-Gear, a filtering system marketed by ICL which uses DDR. I-Gear is stored on the school’s Internet server and monitors incoming and outgoing traffic. Paul Mercer, director of IT says: “It carries lists of banned sites and examines text before displaying it. You can also program the software to display a fixed percentage of a page. We’re very pleased with it.” But even Mercer sees the inconsistency of some filtering: “Rap music sites are a problem because many songs contain offensive lyrics and yet some of our year 11 pupils might be studying rap for a music project. The ironic thing is that the kids can go home and listen to the lyrics on a CD.”

Clark says RM is looking into offering multi-level filtering so that schools could give varying levels of Internet access to different age groups. And Carey believes that in time, more schools will have to take over the task of filtering. “It’s such a massive job and ISPs need computers with enormous processing power to cope with the volume of data,” he says. “The advantage of school-based filtering is that teachers would have a greater control over what their pupils can and cannot see.”

Further information

I-Gear costs from pound;1.50 per pupil from ICL. Tel: 0117 984 2018