Experts give tips on recognising ADHD:

It's easy to label a child who constantly misbehaves as a problem child - but the truth may be that the child can't help misbehaving, because their problem is ADHD (attention deficit hyperactivity disorder).

The genetically-determined condition is thought to afflict around three to seven per cent of school-age children, but it often remains undiagnosed. Only one to two per cent of children are diagnosed, and many of the remainder don't get appropriate support and exhibit such problem behaviour that they are excluded from school.

Children with ADHD show disruptive behaviours which can't be explained by any other psychiatric condition, and are more extreme than simple misbehaving.

They have difficulty focusing their attention to complete specific tasks, can be hyperactive and impulsive, and can suffer from mood swings and "social clumsiness".

But the condition doesn't necessarily prevent those who have it from achieving - famous people who are said to have, or are thought to have had, ADHD include Mozart, Pablo Picasso, Elvis Presley, Einstein, John F Kennedy, Tom Cruise, Billy Connolly and Justin Timberlake.

"Every school will have some diagnosed children, and lots of undiagnosed children," says Holly Evans, an educational adviser for ADDISS, the British charity, with that supports the families of children with ADHD.

She explains that it's particularly children with undiagnosed ADHD that are excluded, as those who've been diagnosed have an 'official' disability and shouldn't be excluded under the Equality Act.

She says they still are excluded, but if parents contest the exclusion it's usually winnable at a disability tribunal.

"Children tend to be excluded because teachers don't understand the nature of the condition and think they're being wilfully naughty, as opposed to having a disability," she explains.

ADHD is caused by a combination of factors, including changes in the parts of the brain which control impulses and concentration, and genetic and environmental factors.

Problems often arise at school with ADHD children because they're impulsive and emotionally immature.

"They'll get upset with someone, but they can't walk away and because they're impulsive they might hit them," says Evans.

"They make the same mistake over and over again, so schools start to feel exasperated as they put interventions in and they look like they're not making any difference.

"They don't understand that children with ADHD need a lot longer for interventions to work."

She explains that those with ADHD don't have the inner voice that tells normally-functioning people how to control their daily life such as by getting to school/work on time, learning from the past, and understanding time periods.

Children with ADHD have a working memory deficit and can't learn from the past, or predict the future.

They may have lots more energy than other children, and while they have difficulty concentrating, they can concentrate on the things they love, a symptom of ADHD called hyper-focusing.

"If teachers understood these difficulties, then they'd change their expectations, and kids with ADHD wouldn't end up in so much hot water," stresses Evans.

She says schools need to have realistic expectations about the interventions they use, which might include specialist cognitive behaviour therapy (CBT) programs, or mentoring.

Evans says the condition is more likely to be dealt with inappropriately in secondary schools, as in primary schools there will be other children who have similar difficulties just because they haven't matured.

In secondary schools an ADHD child's emotional immaturity "will stand out like a sore thumb", she stresses, and this may eventually lead to exclusion.

"There are lots of good schools that try really hard with these kids, but there are also lots that don't try as hard and just think they'll get rid of them.

"There's such a misunderstanding about what ADHD is - teachers often don't understand that the condition affects children's learning and the way they process information. They think it just affects their behaviour."

She says parents often feel their child isn't just misbehaving and has ADHD, because they realise the child can't help their behaviour.

"These children act without thinking, and when it's pointed out that they've done something they shouldn't, they're usually quite apologetic and promise they'll never do it again - and then of course they do it again five minutes later.

"It's working out whether they've done it on purpose or they can't help it. For parents and teachers it's about knowing and understanding the child."

She says that, conversely, some parents may think their child has ADHD, when in fact their behaviour is linked to parenting, abuse or just having a tough time.

"They have ADHD-type symptoms, but with the right interventions, those symptoms can go away. But if a child has ADHD, the symptoms will never go away, you just manage them."

Children with ADHD aren't choosing to be in trouble all the time, and they'll often become anxious about their behaviour, she says.

"Lots of parents are relieved when their child is diagnosed with ADHD, because they realise it's a neurological disorder and not about how they've been parenting.

"But there's still a stigma attached to it, and some parents are embarrassed.

"It's never going to be an easy ride if you've got an ADHD child, but with the right parenting, the right support from clinicians and teachers who are aware of the condition, they can do well and be successful adults."