A teenage girl has her fingers entwined in those of the baby in her arms, as she nervously waits in the school corridor for the next class to start. The door opens and she goes into the classroom where 20 pupils wait for her to begin the lesson on sex education.

Lisa Fell, teacher for a day, was only 15 when she became pregnant with her son, Reis, now six months old. She has joined forces with her friend Emma Whitehead, who has a three-month-old son, to warn other teenagers about the pitfalls of early motherhood. Their message is not a moral, but a practical one: motherhood at 15 is not easy.

When Emma and Lisa had the idea of making school visits they contacted a large comprehensive in Birmingham. After giving the idea some thought, the teachers decided that the scheme would work as part of their sex education policy

Lisa and Emma are not much older than the schoolchildren in uniform but their responsibilities have put them a world apart from their audience. Laden with bottles, dummies and nappies, the young mothers settle on two plastic chairs. The unease is infectious; along with the other teenagers they too are blushing and fidgeting.

Reis has a perky face and a cheeky smile. Lisa holds him up high for everyone to see. The response is one of admiration - sentimental coos and aahs ring out. One girl slides her finger into Reis's half-clenched fist and when he grips it her face goes red, bringing laughter back to the room.

Gary Llewellyn, deputy head at Ninestiles School in Acocks Green, walks around the chairs, listening, nudging the children along when the lesson goes slightly off track. Lisa is still holding Reis up. 'Lovely, isn't he?' she says. The class agree, but are taken aback when Lisa's attitude turns bullish.

'Well you wouldn't think he was lovely if you'd been with him at three o'clock this morning. He's a full-time job and there's no one around to take him off my hands when it all gets too much.'

Emma, whose son Andrew is three months, butts in: 'Do you lot like going shopping?' There are murmurs of agreement. 'Well, don't think you can go shopping easily if you've got a baby. It takes ages to get all the stuff together to take with you. And when you're ready to leave, there isn't time to get yourself looking good. You go out and people stare and look down on you for having a child while you're still a child yourself.'

Teachers hope that this plain talking will encourage schoolchildren to think more about how a sexual relationship can lead to unwanted pregnancy.

In recent years the numbers of teenage pregnancies in the area covered by the West Midands Regional Health Authority have remained relatively constant, but the figures continue to cause concern. In 1992 more than 130 girls in Birmingham aged between 11 and 15 became pregnant; in the whole of the West Midlands region, it was nearly 550. Of that number, 75 per cent were terminated. More than 70,000 teenage girls give birth each year in the UK, but the Government aims to halve the rate of pregnancies among under-16s by the year 2000. Later this month a radio campaign will remind parents of their role in teaching children about sex.

Emma and Lisa fought hard to keep their babies. 'My boyfriend and I were 15 when I fell pregnant. I couldn't believe it. You never think it's going to happen to you,' says Emma. 'When I told my mum she went mad. She said 'You've ruined my life. How could you do this?' Everyone was talking about who would pay for the abortion, but nobody asked me about it. I didn't want an abortion. I wasn't allowed to see my boyfriend. It was a terrible time.'

Emma and Lisa now live in a hostel for young mothers on the outskirts of Birmingham. The babies' fathers are still around but cannot provide financial support.

Emma's boyfriend, Stewart Dutton, remembers being worried at the prospect of being a father. 'When I told my mates they said, try to get rid of it straight away. I'm glad we didn't. I can't support Emma and Andrew, but I'm studying really hard at college so that I can be a chef or waiter. I used to mess about at school but now I take studying much more seriously.'

Stewart approves of Emma's visits to Ninestiles. 'I think I might have messed about if a girl with a baby came into my class. But if the class can be made to sit down and listen and take it seriously then it might work.'

The lessons Lisa and Emma give are for boys and girls, and it is the boys who tend to be the first and most eager to ask questions. Some look worried as they study the two mothers and their babies.

Fourteen-year-old Simon Flynn asks: 'Would you like to put Andrew in a kind of bank if you could, lock him away, then open the door in say 10 years' time and have him back just as he is now?'

Emma says his question shows he understands her and Lisa's message and she agrees that she would use such a bank if it existed.

Robert Long, 15, says: 'I think there should be sessions like this in every school. I knew before that it was important to use precautions but this gets it across even more.'

Emma constantly reminds the class how much of a sacrifice she has had to make for her mistake. She says: 'I had so many plans. I was going to be one of those women wearing a suit with padded shoulders and holding a briefcase. That's all gone now. I hope to take my GCSEs later, at college, but I don't know how I'm going to sort out the childminding. 'I love Andrew, but it wasn't fair on him or me to have had him while I'm so young. I really want other kids to know what a big mistake it is and to take precautions.'

Lisa says: 'If someone like me had come to my school when I was 15 and said the things I say now, then life could have turned out differently. Reis is great, but it was far too early for me to have a child. Nothing would have stopped me having sex with my boyfriend but I would have made sure we used condoms. I was too embarrassed before to go into a chemist. I was frightened a friend of my mum's might see me and tell her. I didn't have any sex education and I think that's why I'm in this situation.'

Birmingham City Council's health education unit already invites people into schools to talk about their 'real life' experiences but it was not involved in planning this project. The department regards it as a useful teaching method, but one that needs to be used with caution. Lisa and Emma are caring mothers, whose babies seem happy and healthy, and the school and health education unit are aware they could portray too attractive an image of teenage motherhood. But the girls are conscious of this, and try hard to describe their feeling of loss.

Teachers are advised to monitor sessions closely because unsuitable messages could come across, such as that early motherhood is merely a fulfilling and joyful experience. Moreover, regularly inviting people such as Emma and Lisa could be used by schools as a way of allowing teachers to avoid their obligations to provide sex education.

Gary Llewellyn is always involved in these classes, called personal and social education. 'I've planned many visits to the school in the past but nothing as unusual or as popular as this one. I asked the teenagers taking part to write essays about how their parents responded to the idea and there wasn't a single negative reaction.

'I don't know how they deal with this subject in other schools but they would do well to repeat the technique. I'm sure this will have a lasting effect on these teenagers - it's not just school-time pregnancies we're addressing but pregnancy throughout the early years.'

(Photographs omitted)