Parents and teachers need to watch out more carefully for head injuries in children, a UK charity has warned.
A head injury may not always be apparent
The Children's Trust said acquired brain injury is a cause of hidden disability in children and it often goes undiagnosed.
It is estimated 5,000 children a year may sustain brain injuries which put them at risk of co-ordination and memory problems.
Causes can include a bang to the head, near choking or drowning and illness.
According to guidance published earlier this year from the National Institute of Clinical and Health Excellence, many more will be living with the long-term effects.
On the surface children with a brain injury may look and behave normally until they are put under pressure or face a situation they are unaccustomed to, such as the transition from primary to secondary school, it is said.
Launching a campaign to raise awareness of the condition and its symptoms, Fiona Adcock spokesperson for the trust said: "Getting used to the transition to secondary school can be difficult for any young person.
"But for those with an acquired brain injury it's around this time of year that any difficulties they have in thinking, making friends and managing their behaviour in class can start to have a major negative impact on their lives."
She said parents and teachers need to be vigilant and support any child they think may have sustained a brain injury in the past.
Common effects to look out for include a shortened attention span, memory problems, extreme fatigue and problems with co-ordination or balance.
Luke Griggs, spokesperson for Headway UK, the brain injury association, said: "Brain injury is often known as the hidden disability as often there are no obvious physical signs.
"Early intervention and treatment for a head injury is very important for a good long-term prognosis, and it is always wise to seek medical attention if in any doubt as to the seriousness of a head injury.
"Brain injury can have devastating effects on lives, and the more we do to raise awareness of the issue, the better."
He added there were signs to look for when checking for concussion following a head injury, such as whether the injured person appears to be dazed or confused, has double vision, answers simple questions slowly or has an increased sensitivity to light or noise.