he worlds of computers, television and the Internet have just grown closer as Britain gets its first digital television services. Last month, the BBC started broadcasting four channels of digital television - even though the equipment to view it is not yet available. This month, Sky’s digital satellite service offers 200 television and audio channels. And other digital tevision services will follow.

But what has digital TV got to do with information and communications technology, and why should schools be interested? The answer is: its enormous educational potential to convert the classroom set into an interactive or two-way device. Until now, television has been an analogue system, with pictures and sound broadcast as an electronic wave and, apart from teletext services, there is little interactivity with the screen. But digital TV transmits programmes in the form of computer code.

“It will allow us to integrate all the things we do today into one seamless system,” says Jonathan Drori, the BBC’s head of digital media and learning channels. For example, the Internet could be linked with the television. Imagine watching a geography programme on Mount Everest. Click on a small on-screen icon and you are taken instantly to a website where you can find more information on the Himalayas. This isn’t fantasy, BT and the BBC are testing Microsoft’s WebTV system, which offers this facility.

All digital set-top boxes will include a modem and link to a telephone line. BSkyB will offer many interactive services through British Interactive Broadcasting, owned by BSkyB, BT and others. The BBC is planning to launch a new educational channel on digital television next spring. Provisionally called BBC Learning, it will be aimed at children, parents and adult learners.

Large media groups are already forming links between television and the Internet. The BBC runs BBC Online, which includes many Web pages for students and teachers. Granada Television is partner in a new digital service, ONDigital, and owns an educational software company, Granada Learning. Anglia Multimedia, whose educational offerings include software titles and the Anglia Interactive website, is part of the United News and Media Group, which has television interests.

The Department for Education and Employment has issued a consultation paper to various media groups asking them to suggest ways that digital television could be used in education. The department has also launched a tendering process, the results of which were expected to be published this month. “The potential of digital is most certainly there,” says Peter Stibbons, Anglia Multimedia’s director of development.

Digital TV could also be delivered to suitably equipped computers. This opens the way to transmitting large amounts of data directly to a computer hard disk. Anglia Interactive posts CD-Roms to its subscribers, which are then put on to the school’s computer server. The CDs contain video material and other files which are too large to send over the Internet, but a digital TV delivery system could save both time and postage costs.

The digital versions of the Ceefax and Teletext services will be much improved, with pages offering more colours, better text, more graphics, faster links and even photographs. But both companies are keen to maintain their services’ simple-to-use operation.

The cable giant Cable and Wireless has bought a large stake in Two-Way TV, an interactive system that allows text and graphics to be superimposed over a television picture. Multiple-choice questions can be answered by pressing a button on a remote control handset. Cable and Wireless plans to use Two-Way TV in its new digital TV service, due to be launched next year.

The BBC’s Jonathan Drori says schools should be excited about digital TV, but warns: “Real interactivity in the way you can do on the Web today, won’t come through your television in the early days. Today’s Web pages are designed for a computer, keyboard and mouse, and not a television and remote control handset. ”

Peter Stibbons points out that most school programmes are watched in groups and that interactivity suggests one television per child - an expensive exercise. He adds: “Most educational programmes are recorded these days, and you would lose any interactive elements. We need to talk to teachers and find out the best ways of using this technology.”

These are early days for digital TV, but with some digital services delivering hundreds of new channels into homes and schools, and offering new interactive services, schools broadcasting may never be the same again.