According to a Freedom of Information (FOI) request by the BBC, police gave a record of sexual offences at schools during last three years, from 2012 to 2015.
The figures recorded by FOI request states that these included nearly 4,000 indecent assaults and more than 600 rapes.
More than 1,500 victims were under 13 and most were primary and secondary school students. At least a fifth of the offences were carried out by children, so-called "peer-on-peer" abuse.
"I believe these figures are the tip of the iceberg. "It is a good news that more victims have the confidence to come forward and report abuse, although - while I cannot prove this...I believe more child abuse is taking place," National Police Chiefs' Council lead for child protection, Chief Constable Simon Bailey was quoted as saying by BBC.
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"These figures are very disturbing, especially as many victims are so young and the reported offences took place on school premises. Sadly, we are not surprised as previous NSPCC research has illustrated the scale of abuse committed by young people," Jon Brown, head of Sexual Abuse Programmes at the National Society for the Prevention of Cruelty to Children (NSPCC) said.
"I want Personal Social Health Economic Education with a relationships and sex component to be part of the national curriculum. Every child needs to understand what is inappropriate or illegal behaviour."
According to the latest Department for Education statistics in England, 60 children were permanently excluded for sexual misconduct in schools in 2013/14. There were no exclusions in Wales and Scotland. Northern Ireland was unable to provide figures.
Sex and relationships education is compulsory in maintained secondary schools and many primary schools also teach it in an age appropriate manner, but campaigners say it doesn't go far enough.