And as Panorama reports in Kids Behaving Badly, children are being subjected to a type of bullying which makes it even harder to speak out - sexual bullying.
This can be anything from sexualised name-calling to spreading rumours about someone's sexual behaviour, to criminal offences such as assault and rape.
Though it may be hard to believe, in schools all around the country - even primary schools - children are being sexually bullied and assaulted by their fellow pupils.
The most recent government figures show that from 2006-2007 there were 3,500 exclusions from schools in England for sexual misconduct - anything from explicit graffiti to serious sexual assault - the equivalent of 19 per school day.
'Assertion of power'
But as Panorama reports, all too often cases go unreported or are written off as children experimenting.
"I think it's really difficult for people generally to think about sexually harmful behaviour happening by young people, towards young people in schools. But it is an issue, it is happening, and we need to acknowledge it and we need to respond to it," Paula Telford, from the NSPCC tells the programme.
Michelle Elliot, from the anti-bullying charity Kidscape, says that "sexual bullying has almost become a way of asserting your power over others and for that reason it is disturbing".
To get an idea of just how prevalent the problem is, Panorama worked with the charity Young Voice to question youngsters aged 11-19 about their experiences.
Of the 273 youngsters who answered the questionnaire, 28 children said they had been forced to do something sexual they did not want to do.
One girl in the North West said she was forced to perform oral sex on a fellow pupil and one girl said she had been raped.
The NSPCC says such experiences are not unusual:
"We've had examples for instance of a 16-year-old boy who raped a much younger boy in a secluded setting in school," Ms Telford tells Panorama. "We've had a 10-year-old who was forcing other children to perform sex acts on him, and performing sex acts on them. And we've had much younger children who've been inappropriately touching each other."
But even in the most serious cases, those responsible are often not being prosecuted or even counselled.
A 13-year-old girl tells the programme that she was subjected to steadily worsening sexual bullying by a boy in her school, which went on for months until she told her parents.
Her mother contacted the school and was told the boy would be spoken to and a letter would be sent to his parents, but he was allowed to remain in the girl's class and no further action was taken.
It was only when the girl and her family reported the allegation to the police that the boy was made to switch classes - a situation which left the girl's mother in despair:
"It's inconceivable that somebody could be sexually assaulted and expected to go to school with them and be next to them or near them in a classroom," she says.
But even when the school does take the matter seriously, it can still be the case that the perpetrator is better supported than the victim.
Panorama speaks to the father of a 15-year-old girl who was lured into an empty classroom where a group of boys, also pupils at the school, forced her to perform oral sex on one of them.
The girl spoke out about the incident and her head teacher was quick to refer the matter to the police.
However, when the girl was too traumatised to return to school and her parents turned to their local council to arrange home tutoring, they were told that this facility was reserved for children who had been excluded from school such as the boys who had assaulted her, not their victims.
And as Panorama learns, the consequences of sexual bullying in schools may go much further than the distress it causes at the time.
"When you look at the backgrounds of some adult sex offenders, you do see inappropriate sexual behaviour when they are younger, as well as other indicators. It doesn't mean that every child who acts out sexually is going to become a sex offender, but we ignore it at our peril," Ms Elliot from Kidscape says.
Panorama: Kids behaving badly on BBC One at 8.30pm on Monday 5 January 2009.