Bullied teenagers attain significantly lower exam results than other children, according to a study that claims to prove a statistical correlation between abuse at school and educational achievement for the first time.
The GCSE results of children bullied at 14 or 15 are two grades lower, and their total score is 13 fewer points, the government-backed report says.
It also found victims of bullying were less likely to attend school full- time at 16, and that more became Neets - not in employment, education or training.
The study, "The Characteristics of Bullying Victims in Schools", claims it is the first in-depth investigation of the impact of the problem on GCSE- age pupils. Researchers studied 10,000 children; the full findings are due to be published in January.
Almost half of the 14-year-olds who took part said they had been bullied; this figure fell to 41 per cent at 15 and 29 per cent at 16.
The most common type of bullying at all ages was name-calling and cyberbullying, followed by being threatened with violence, social exclusion and being attacked.
Bullies were most likely to target those with special educational needs, young carers, pupils with a disability and children in care.
Girls were more likely than boys to be bullied at age 14 and 15, although gender became less important at 16. Girls were also more likely to use name-calling or excluding from friendship groups, while boys were much more likely than girls to have their money or possessions taken, to be threatened with violence and to be attacked.
Previous studies have established that bullying victims have lower self- esteem and are at greater risk of suicide but have not examined the link with academic performance.
All schools are now required to have anti-bullying strategies. Several pilot schemes have been given funding by the Department for Children, Schools and Families to run programmes to discourage bullying.
Peter Smith, head of the Unit for School and Family Studies at the University of London's Goldsmiths, said any analysis of the academic record of bullying victims must take into account the fact that many would have special educational needs.
"It's clear bullying creates lower self-esteem and this affects school performance, so you could see causation in lower GCSE results," said Professor Smith, who is currently completing a DCSF study on how effective schools are at preventing bullying.
"There are all kinds of factors associated with bullying which could contribute to not doing as well in exams. Unhappiness and depression affect children's work, too."
But Richard Piggin, head of operations at the charity Beatbullying, said he had met many young people who described having to "dumb down" to avoid being picked on.
"They don't want to be seen as different, and that goes for those with a particular talent in music or sport too," Mr Piggin said.