I have learned to dread those occasions when I’m stuck at the hairdressers or in the back of a taxi and get the inevitable polite question: “So, what do you do?” I used to explain that I’m a university researcher working on specific language impairment (SLI), but that invariably drew a blank look, or questions about children who stutter or have English as a second language. I have now learned to say that I work on conditions such as dyslexia and autism, and I can be fairly confident that most people will know what I am talking about.

But this is rather odd. SLI is a pretty common developmental problem - similar in frequency to dyslexia and much more common than autism. In fact, most teachers are likely to have at least one child in their class with this kind of language difficulty. So why hasn’t anyone heard of it?

I suspect that part of the problem may have to do with professional boundaries. In contrast to autism and dyslexia, SLI - quite apart from being a bit of a mouthful - lies squarely in the domain of speech and language therapists, a female-dominated profession with little clout. The typical lay person has little idea of what these therapists do, and if asked is likely to refer to stuttering and The King’s Speech. Although some speech and language therapists work on stuttering or articulation problems, much of the work done with children is focused on language skills: using words to express or understand meanings.

So what does SLI look like? It’s identified when a child’s spoken language is out of step with other aspects of development for no obvious reason. The easiest kind of SLI to spot is the young child with expressive language difficulties, who uses simple language with short sentences and limited vocabulary. For instance, you might notice that a five-year-old says “him go there” rather than “he went there”, with language that sounds more typical for a three-year-old. But for older children, a language problem may not be obvious without a proper assessment by a speech and language therapist. The child may have difficulty producing or understanding long and complicated sentences, and just guess at what has been said by picking out one or two familiar words.

Children with SLI can hear normally, but have problems making sense of what has been said. Some children complain that they just can’t keep up, especially in the confusing environment of a busy classroom. It’s easy to see how such a child would not only fall behind at school, but would also run the risk of being identified as lazy or disobedient.

Another clue is if a child struggles with learning to read. Although for many children this is a specific problem with written language, some children who are labelled as dyslexic do also have problems with understanding or producing spoken language.

It is important that teachers are alert to this possibility, as such difficulties can be overlooked if attention is focused on the more obvious problems in decoding print. A referral to a speech and language therapist can help identify areas of specific difficulty, and make it possible to devise intervention strategies that will maximise the child’s abilities.

John Bercow’s report (bit.lyRGboNF) in 2008 stimulated a great deal of interest in children with speech, language and communication needs, yet much more needs to be done. The impact of SLI on the child and the family is often serious: the language impairment frequently affects social interactions, educational attainments, and ultimately the ability to participate in society and hold down a job. Yet because SLI is a hidden disability, it often goes unnoticed and children’s needs are neglected. And once children with SLI move into adulthood, they miss out, because they don’t have a recognised disability for which support services are available.

Last year, I joined forces with fellow academics Maggie Snowling, Courtenay Norbury and Gina Conti-Ramsden and with speech and language therapist Becky Clark to form a group called Ralli - Raising Awareness of Language Learning Impairments. Our goal is simple: we want awareness of SLI to be as widespread as awareness of dyslexia and autism. We see it as crucial to have better recognition that children may have talents that can be fostered, even if their language difficulties limit their ability to access the mainstream curriculum.

With the support of funding from the Waterloo Foundation, Afasic Cymru and the Economic and Social Research Council, we set up a YouTube channel that went live in May. We’ve been delighted at the interest that the channel has attracted: not just from the UK but from all over the world. It’s clear that the Cinderella status of SLI applies to children learning many different languages, and not just English.

Over the coming year we will post further videos that will give information and background about SLI. We plan a mixture of content, ranging from interviews with children and their parents affected by SLI through to brief summaries of recent research.

We will be posting videos to help teachers spot possible language difficulties in children in their classrooms, videos sharing teachers’ views, as well as clips of pupils themselves telling about their experiences in the classroom and how teachers can help children with SLI.

Please do look at Ralli and spread the word about it. These children have been ignored for too long.

Dorothy Bishop is professor of developmental neuropsychology at the University of Oxford. Visit www.youtube.comRALLIcampaign for more information about SLI.