Young carers: Quarter of a million children provide care for others
Nearly a quarter of a million children in England and Wales are caring for a relative, new statistics show.
Figures from the ONS suggest 244,000 people under 19 are carers - about 23,000 are under nine.
The Children's Society warns this is likely to be "the tip of the iceberg" and that children's education and job prospects could be damaged.
The government says schools have a "key role in supporting young carers".
According to the ONS (Office for National Statistics), there are 149,000 young carers aged between 15 and 19 - about twice as many as in the 10-to-14 age range.
Girls are slightly more likely to be carers than boys. Among 15-to-19-year-olds, about 5% of girls are carers and about 4% of boys.
The Children's Society is calling for more government support and recognition for these young people.
It says in England, one in 12 young carers spends more than 15 hours a week looking after a parent or sibling, that one in 20 misses school and that they are 50% more likely to have special educational needs or an illness.
In its report, called Hidden from View, the Children's Society says: "Many young carers remain hidden from official sight for a host of reasons, including family loyalty, stigma, bullying, not knowing where to go for support."
The study, funded by the Big Lottery Fund, analyses government data that tracked 15,000 children in England aged 13 and 14 between 2004 and 2010.
It found young carers had "significantly lower" educational attainment at GCSE level - the equivalent to nine grades lower overall - than their peers.
The study found average annual income for families with a child carer was £5,000 less than families that did not have a young carer.
Young carers were more likely than the national average to be "not in education, employment or training" (Neet) between the ages of 16 and 19.
Young people from black, Asian or other minority ethnic communities - and for whom English is not a first language - were twice as likely to be a young carer.
The Children's Society says that, despite improved awareness of the needs of young carers, there is no strong evidence that young carers are any more likely than their peers to come into contact with support agencies.
The report says: "Children must be allowed to thrive and enjoy their childhoods, not be forced to take caring roles that are too often inappropriate."
Children's Society chief executive Matthew Reed said: "Our new analysis shows that caring can cost children dearly. They are missing out on their childhoods and school, gaining fewer qualifications and therefore are less likely to earn a decent living.
"All children must be allowed to thrive and enjoy their childhoods. One young person remaining under the radar, out of sight of the very authorities there to support them, is one too many."
A Department for Education spokeswoman said: "Schools have a key role in identifying and supporting young carers. We must ensure that every child has the opportunity to meet their full potential.
"We recently announced that young carers will be involved in the training of school nurses, so they know exactly what support they should offer and can champion their needs.
"We are also funding the Children's Society and Carers Trust to encourage children's and adult's services to adopt 'whole family' approaches to supporting young carers and we have created a specific training guide for teachers to help them to better identify and support young carers."
The Disabled Parents' Network says it is important to remember that behind every young carer is at least one parent with a disability.
A statement on the charity's website says: "DPN rejects the notion that disabled parents are a problem to be solved.
"It is a simple fact that if disabled parents are provided with the support packages to which they are statutorily entitled, then there is less need for their children to assume the role of 'young carers'."