It was not the first children’s television programme to combine education with entertainment. After all, Blue Peter set out to broaden its viewers’ horizons. But 40 years ago next week marks the debut transmission of a show where teaching was a fundamental part of its remit.

Sesame Street, which first aired on US television on November 10, 1969, was born out of extensive research into how children learn and was the first programme to have its own curriculum. According to Malcolm Gladwell, author of bestseller The Tipping Point, the show “was built around a single, breakthrough insight: that if you can hold the attention of children, you can educate them”.

The show’s mixture of live action, puppets and animation aimed to help young children prepare for school through a range of tools, from letter and number recognition to social skills. Research carried out after its first season found that regular viewers were 62 per cent more likely to recognise a rectangle than less frequent watchers.

Despite such a longstanding pedigree, however, television as an educational tool is still a contentious subject. Instead, the medium is held responsible for a range of ills, including hampering social skills, drawing children away from other, more “constructive” pursuits and rising levels of obesity.

Last month, the Australian government urged parents and childcare providers to prevent children aged under two from watching television at all, and to limit two to five-year-olds to one hour a day. Guidelines were drawn up on the advice of medical researchers. French channels were last year banned from airing shows aimed at under-threes on the basis that television encouraged passivity, slowed language acquisition and affected sleep and concentration.

And just last week it emerged that American parents who had bought Disney’s Baby Einstein DVDs were being offered refunds after researchers found they had no educational value.

But this has not stopped many teachers using television as a teaching tool. From dedicated children’s programmes to filmed adaptations of set texts, TV has been a classroom staple for many years. Even with young children, teachers have seen benefits from using the medium.

“It can be a really good stimulus,” says Rebecca Sowden, a reception teacher in Newcastle. She cites a recent lesson where she showed her class a video of Winnie the Witch. “They fell in love with the story and they all wanted to read the books,” she adds.

The use of television should be balanced with a large range of text-based activity, she says, but there is no reason why it should not form part of a teacher’s repertoire.

Programmes such as Fun with Phonics that introduce children to sounds as the foundation of literacy, and Razzledazzle, a storytelling show, both aired on pre-school channel CBeebies, can be useful educational tools, she adds.

But she believes it is important to control the use of television. Some young children can struggle to understand the themes of programmes ostensibly aimed at them, and she says care should also be taken in exposing children to advertisements.

“It (TV) needs to be under supervision and with thought. Even with some of the programmes on the Disney Channel the themes can be too adult for my class of four-year-olds and I worry about the consumerism,” she says. “They are bombarded with images that are creating needs and desires that they would not necessarily have.”

Neil McGregor* was worried about the amount of time his five-year-old daughter, Eve, spent watching television. Whenever her friends came over, Eve was glued to the television while they played around her. But now he takes a more relaxed view.

“She comes out with some unusual words and I used to wonder where she got them from,” he says. “She obviously understands what they mean, and eventually I realised she was picking them up from the television.

“She loves reading books as well so it’s not as if she only watches television, but now I think if she wants to sit in front of it, it isn’t really doing her any harm and might actually be doing her some good.”

Research carried out in Texas and published earlier this year found that even long hours watching television had no impact on academic achievement among primary pupils.

The study looked at the viewing habits and grades of children from reception to Year 6 but failed to find a link between the number of hours watched and school results, although researchers did warn this might not emerge until adolescence.

In the days of extended schools and widespread after-school activities, there can be another advantage to television, argues Anthony David. “Television is good at allowing children to have a bit of downtime, and if it’s regulated I don’t think that is a bad thing.”

Mr David, deputy head of Highgate Primary School in north London, says that it is important to be discriminating, particularly now that there are numerous channels targeted at children. But provided it is used sparingly and under supervision, he believes that TV can be a useful tool with young children.

“It is really easy to use the electronic nanny as a way of keeping children quiet, but it does have to be carefully used. I don’t necessarily believe that children pick up vocabulary from television, and talking to children and spending time on shared activities is by far and away the best thing you can do,” he says.

He believes that the issue of how much screen time children are exposed to extends beyond television as a result of the proliferation of games consoles such as PlayStations and the Nintendo DS and entertainment applications for mobile phones.

“I have just been away on an outward bound trip with 44 Year 6 children and it was interesting to see the children who wanted to take electronic devices,” he says. “You can predict those children who will have a greater screen-time allowance at home.”

Figures from a National Statistics time-use survey found that eight to 15- year-olds spend an average of two hours 20 minutes watching television, about half an hour less than the average adult.

A survey for energy firm npower earlier this year found that seven to 16- year-olds spent an average of nearly 10 hours a day looking at screens, including using computers at school, mobile phones, games consoles and iPods.

When asked in a 2007 survey which type of media they would miss the most, 64 per cent of five to seven-year-olds and 52 per cent of eight to 11- year-olds nominated the TV. It was only among 12 to 15-year-olds that mobile phones and the internet mounted a challenge, with 25 and 24 per cent, respectively, to TV’s 29 per cent.

But the French and Australian governments are not the only ones to be urging stricter limits on screen time, particularly for younger children. In some cases, it is not just poorer concentration and disrupted sleep that is seen to be at stake.

Research carried out in the US appears to show that for children under two, every hour in front of the TV increases their risk of developing attention deficit disorder by 10 per cent.

Although it is possible that it was the child’s attention problems that attracted them to the TV in the first place, the weight of evidence firmly comes down against young children watching television, according to Aric Sigman, a psychologist and author of Remotely Controlled: How Television is Damaging our Lives.

After reviewing 35 studies on the impact of television, Dr Sigman identified 15 effects, from an increased risk of diabetes to subverting the development of brain cells. “The evidence is very directly against children watching any electronic media, whether television or any other form, below the age of three,” he says.

This applies equally to educational programmes, he says, irrespective of quality. “Without question these do not in any way, shape or form enhance a child’s vocabulary. They do the opposite.”

While the information children are exposed to may add to their knowledge, this is outweighed by the effect on brain development, he says. Watching television undermines children’s ability to pay attention and there are strong links between hours spent watching TV and low rates of literacy, he adds.

Even when children do not start watching until the age of three, he says, there is a negative correlation with school achievement once they watch an hour-and-a-half or more a day.

This is not to say children should not watch television at all. Dr Sigman says it can be a useful recreational tool. But he is sceptical of claims that it has an educational value. “Does a modest amount of television add to children’s knowledge? It does, but you have to ask if it is not something they could have learnt from a book,” he says. “Television does the work for them, so the brain doesn’t have to work very hard.”

But the problem is not the television itself; it is the way it is used, argues John Siraj-Blatchford, of the faculty of children and health at the Institute of Education, part of London University. Writing in The Guardian last month, he says that while solitary viewing is at best a distraction from verbal interaction, where parents watch programmes with their children, the children tend to gain more from the experience. “Television and home computer programs often provide valuable contexts for rich verbal interaction and this is something we can promote,” he writes.

As with most things, the answer is balance, argues Georgina Mountjoy, a primary teacher in Bristol. This term she used a film adaptation of Oliver Twist to support lessons about the Victorians, while some children have independently been watching the documentary Victorian Farm and applying that to their writing, she says. “In some respects, TV can be a very useful teaching tool,” she says. “The film really engaged and inspired them and offered an inclusive, visual teaching tool.”

But she says the most articulate children she has taught have been those with lots of access to books and who have read with parents from an early age. And in order to learn from television, children need to have the images and information explained to them, she says.

“Children learn in different ways and need more stimulus than a television programme.” While television can be inspiring, it is only really useful if it is used alongside other resources, she adds. That’s probably something even Big Bird would agree with.

*Name has been changed

Classic TV of yesteryear

• Scene: A long-running social education programme, covering issues from drugs to finding a job.
• Look and Read: A cult series aimed at seven to nine-year-olds combining an adventure story with grammar. It was presented by Wordy, an orange character with letters on his body. Stories included Cloud Burst and The Boy from Space.
• Landmarks: A history series first shown in the 1980s, ranging from the Gunpowder Plot to environmental concerns.
• Everyday Maths: Applying numbers to everyday situations.
• How We Used to Live: Historical drama tracing the lives of Yorkshire families in the fictional town of Bradbury.
• Stop, Look, Listen: An introduction to social science narrated by Chris Tarrant.
• Believe It or Not: A long-running religious series introducing children to world faiths.
• Experiment: Chemistry and biology experiments for secondary children, later parodied in the comedy Look Around You.
• Seeing and Doing: Long-running series often looking at multi-cultural or religious issues.
• The Clock: Probably the most memorable part of schools television: the dots on the clock vanished one by one in the countdown to transmission.