Dorothy Bishop had her epiphany in the back of a taxi.

“The taxi driver, the way they do, said, ‘What do you work on?’” Bishop recalls. “I said, ‘Specific language impairment,’ and he had no idea what that was. He thought it might be something to do with learning a second language.”

So she decided that the best way to explain language disorders was to say, “It’s a bit like autism.”

“And the idea that he could immediately know what autism was - even though it’s a much rarer condition - seemed something quite wrong,” she says.

Wrong - but all too common, she quickly realised, even within the education system.

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Bishop is professor of developmental neuropsychology at the University of Oxford. Most of her academic work has been focused on specific language impairment, which is now called developmental language disorder (DLD). She believes that it is the most prevalent special educational need that most teachers have never heard of.

That day, in that taxi, Bishop decided that something needed to change. Too many children were being let down because too few teachers had any idea why they were struggling.

Language barriers

Put crudely, DLD is to spoken language what dyslexia is to written language.

“It can be helpful to say that it’s like trying to function in a language that you have a little bit of knowledge of,” Bishop says.

For example, imagine that you speak a small amount of French: you have some vocabulary, some knowledge of grammar. Then you go to stay with a Parisian family, whose dinner-table conversations take place entirely in French. You can make out occasional words - enough to determine what the conversation is about, but not the details or the nuance.

For instance, if you picked up the words “dog”, “chase” and “boy” in a sentence, you would understand that there had been a chase involving a boy and a dog, but not whether it was the boy chasing the dog, or vice versa.

Understanding what is going on, therefore, requires constant effort and attention: you have to try really, really hard to keep up with what the conversation is - or might be - about. Ultimately, this becomes exhausting, and it is easier to tune out entirely and let the conversation flow around you.

“It’s hard work [for those with DLD],” Bishop says. “Those casual, easy to-and-fro exchanges almost become painful for you to engage with. Whereas everybody else is just chatting away.”

According to researchers in this field, around 7.5 per cent of children begin school with a language disorder that is unexplained by any other condition, with DLD the likely cause. A further 2.3 per cent have a language disorder linked to another condition, such as dyslexia or autism. In a class of 30 children, therefore, an average of two children will need therapeutic intervention for their language difficulties.

This is considerably more than the 1.1 per cent of the population who are on the autism spectrum.

Children with DLD will have higher than average rates of social and emotional behavioural problems, according to research conducted by Courtenay Norbury, professor of developmental language and communication disorders at UCL. They are also more likely than their classmates to have problems with their peers, and problems paying attention. Only around 11 per cent of these children meet curriculum targets.

So these are the children in your class who may have been labelled as underachievers, but whose underachievement will have often been blamed on background, disadvantage or low IQ.

“Often they’re assumed to be children who are just not going to do very well,” Bishop says. “They’d be looking like a very inattentive child who’s a bit away with the fairies. In some cases, there will be bad behaviour, acting up a bit.”

So why is there this collective blindspot where the condition is concerned?

Bishop believes that part of the problem comes down to - perhaps appropriately - language choices.

Until recently, the preferred term for the condition was “specific language impairment”; “developmental language disorder” was settled on only after considerable debate and research.

“All these choices of words are very loaded,” Bishop says. “If I say ‘impairment’ or ‘disorder’ or ‘disability’, it makes a big difference.

“‘Delay’ is often used very loosely to mean that you’ve got trouble with your language. But it doesn’t tell you anything about whether it’s likely to improve or not. It suggests it’s just a delay, but you’ll catch up eventually.”

Difficult to spot

Another issue is that the symptoms of DLD are more difficult to spot than those of many other special educational needs and disabilities, such as dyslexia, as they can be written off as behaviour or attention issues. They may also be more difficult for teachers to understand and empathise with, according to Norbury.

“I think maybe it’s because we take language for granted,” she says. “We all use it. We use language skills to negotiate and to calm other people down. We use it when watching TV, listening to the news, following instructions, talking to your friends, texting, knowing where to get on the Tube. Everything we do involves language.

“People with DLD often come across as not listening or not paying attention. And so people don’t recognise language disorder as much as dyslexia or autism, and it’s really hard for people to convey that this is a problem that needs support.”

Because of widespread ignorance about the challenges they face, students with DLD can have an extremely difficult time in education.

Gemma Corby, special-needs coordinator at a school in Norfolk, encountered DLD when a student was diagnosed with the condition earlier this year, following an appointment she booked with a language specialist. The child had been identified in primary school as having speech and language difficulties, but had not been seen by a specialist for several years.

“He muddles by in school,” Corby says. “But I knew he wasn’t reaching his full potential. He had very high levels of anxiety - I wouldn’t have known, but his dad told me.”

Such “muddling by” is typical for children with DLD, Bishop believes. It is particularly common among girls; boys are more often identified as having DLD, because they tend to misbehave as a result of finding the classroom challenging.

“We think girls [with DLD] just sit quietly at the back of the class, and boys [with DLD] make more trouble,” says Bishop.

In some cases, DLD will go hand in hand with other language disorders, such as dyslexia. But many pupils with DLD are able to read aloud when asked. It is only when asked questions about what they have just read that they struggle.

“Those children, the teachers might not be aware how little they’re picking up as they go along,” Bishop says.

This is another key reason why teachers may not spot children with DLD, according to Megan Dixon, director of literacy for Aspire Educational Trust. She specialises in literacy acquisition, and is, therefore, aware of DLD.

“Often, teachers will spot children who have problems forming phrases,” she says. “But it might be that children with DLD have no problems expressing themselves, but have problems understanding what’s coming in.

“That’s quite hard, because people assume they’re not listening, and they end up being labelled as naughty.”

Alternatively, Bishop says, pupils learn to pass: to scrape by at the bottom of the class. Often, these children are assumed simply to be not very bright.

For example, an eight-year-old pupil may be capable of telling the teacher a story.

“And you think, ‘That’s fine; they haven’t got a language problem,’” says Bishop. “But, when you analyse their sentences, they don’t use any complex clauses. When you compare them with what an eight-year-old ought to be doing, you realise they were quite limited in what they could express. They’ve actually got quite limited language.”

This is something that Dixon has also observed. Early in her teaching career, there was a boy in her class who would not speak.

“He stood in the corner, shivering,” she says. “Literally quivering away.”

Dixon assumed that the boy was on the autism spectrum. His previous school had labelled him as low-IQ, and had held him back in Reception.

“Actually, he had very severe language difficulties,” Dixon says. “Can you imagine sitting in a classroom all day, every day, not understanding, and being told off for not doing things right?”

She believes that children with DLD may be misbehaving deliberately, in order to be removed from class. If this happens, she says, it is a failure of the teacher for jumping quickly to conclusions, rather than looking below the surface of the behaviour.

Unfortunately, better diagnosis of DLD will not automatically improve educational outcomes. Even when pupils with DLD are identified as needing speech and language therapy, this does not guarantee the right help for the right length of time.

Bishop has carried out a series of studies on twins, which demonstrates that there is a genetic component to DLD. There is not, however, one biological trigger - a particular gene that can be singled out as causing the condition. Instead, variations in a range of genes can tip a person one way or another.

Ongoing support

Environmental factors also play a role. Bishop draws an analogy with height: one’s height depends on a complex combination of genetic and environmental factors.

“Your ultimate height might depend on lots and lots of factors, each of which might make you a little bit taller or a little bit shorter, but the individual effects are quite small.”

Therefore, the go-to solution for language problems - a period of intensive speech and language therapy - can often fail to improve things for children with DLD.

“We’ve had this culture of expecting that a short-term blast of speech and language therapy will move children into the normal range,” says Norbury. “More and more, I’ve come to accept that that’s not the case.”

The problem, she says, is that there is often a lot of talk of “closing the gap”. But, by the start of key stage 2, there may be a two-year gap between pupils with language difficulties and those at the top of their class.

“That’s a pretty big gap to fill, particularly as the demands of the classroom get more and more complex,” Norbury says.

“I think education does a fantastic job of moving kids on. But those kids with language problems need ongoing support. If you’ve ever tried to learn another language - you can’t do that in six to 12 sessions. And you have to keep practising. There are no quick fixes, unfortunately.”

There is obviously a complicating factor here. Dixon explains that environmental factors - such as poverty or poor levels of parental literacy - can cause children to manifest many of the same symptoms as children with DLD.

“Teachers often don’t understand that there’s a difference between language delay and language impairment,” she says. “A lot of children are below the level that they should be, that you’d expect, when they’re coming into school. And it can be poverty-related.”

These children tend to be given what Dixon refers to as a “short, sharp intervention”, lasting six to 10 weeks.

“A language-delayed child will hopefully make quite sharp progress. A language-impaired child possibly won’t,” she says.

That short intensive session can still be useful for identification purposes, though. Dixon views it as a form of language triage: they will help sort those children with language delays from those with DLD, who require longer-term support.

Training teachers

But such labelling of a child would not be universally supported. Within the SEND community, the use of labels and the way in which those labels determine what subsequent support is available has been debated extensively.

Regarding DLD, Simon Knight, director of special-needs organisation Whole School SEND and former deputy headteacher at Frank Wise Special School in Oxfordshire, questions whether children would necessarily benefit from having the disorder attached to their names.

“My concern is that sometimes we end up using diagnostic labels naively,” he says. “What are teachers going to do with that information? How are they going to meet those needs effectively?

“If we don’t furnish teachers with a depth of understanding, there’s a risk that they may respond to a caricatured understanding of what that label is.”

There is then a danger, he adds, that certain resources and interventions will become the default means of addressing DLD in pupils, and that these will be used in place of a personalised response to a child’s needs.

“I wouldn’t want teachers to have a veneer of understanding of what needs are in the classroom,” he says.

“We can raise awareness; we can ensure that children are assessed appropriately and effectively. But, if that’s all we do, then children are not going to have their needs met appropriately. So we need to be training teachers as well, to make sure they have the skills necessary.”

Bishop understands the nervousness about attaching labels to children.

Teachers have told her that they are concerned about medicalising normal variation among children, or about being seen as lowering expectations.

But she argues that, used properly, the advantages of such labelling outweigh the disadvantages.

“You hear a lot from paediatricians saying, ‘I’ll give this child an autism diagnosis,’ if the child is on the margins, because then they’ll get help,” she says. “That wouldn’t happen if there was active support for people with other conditions.”

Targeted approach

The label, she believes, would allow for coherent, knowledgeable responses to pupils with DLD. For example, she says, pupils could be given visual support, to help them to access the words that the teacher is using. So a teacher telling the class about windmills, for example, would stand in front of an image of a windmill while talking.

“It sounds horribly like learning styles,” Bishop says. “But it might be that kids have particular difficulty dealing with material where you’re just describing something but there’s no visual support.”

And any speech and language therapy could also be specifically targeted to the needs of pupils with DLD. “With speech and language therapy, a lot of what’s done isn’t being subjected adequately to good trials,” she says. “It’s not that people don’t want to, but they don’t have the resources for trials. Lots of what’s going on in schools is people making it up as they go along.”

In the case of Corby’s student, diagnosis has certainly led to improvements. The pupil has had weekly sessions with a speech and language therapist, as well as daily activities with a teaching assistant trained in dealing with speech and language difficulties.

“He’s still very anxious - not really able to have a two-way conversation,” Corby says. “But on a recent breaktime he came and knocked on my door and we had a conversation. He never would have done that last year. The thought of having to go and have a conversation with someone - especially an adult, and one who wasn’t his tutor. He wouldn’t have done it.”

This student is one of the lucky ones. Too many children with DLD remain undiagnosed, and are condemned to a life of underachievement simply because people are unaware that DLD exists.

“People with autism, when in adulthood, they may be employed, because they have the ability to pass exams,” says Bishop. “But often they wouldn’t have relationships.

“With DLD, often it’s the other way around: they can’t pass exams, so they’re restricted to manual jobs.” She pauses.

“Which, of course, there are less and less of nowadays.”

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