It also explains oral sex techniques, including the “twist and shout” method.
The website was originally meant for 15 year olds, but was also reportedly recommended to children as young as seven in Belgian schools.
Frederic Leire, the father of two children aged seven and nine, said his kids got the guide at school and he was shocked at how explicit it was.
“I would even call it perversities,” he said. “It is great that such a website exists, but I don’t think that children will ask questions like how many sex positions there are and if they need drugs for sexual pleasures.”
The website, launched by Sensoa, was recommended in the “Youth Guide”, a children’s advice guide supported by the Flemish government and distributed across primary schools in the region, according to Belgian media.
The umbrella organisation of Catholic Education also expressed shock, saying the website was too technically focused and did not detail the relational aspect.
Spokeswoman Marijke van Bogaert said: “It is up to the parents to talk about this with their children. We should give 11- and 12-year-olds information about sexuality which is tailor-made for their age group.”
Flemish Minister for Culture and Youth Sven Gatz, however, disagreed and said that those opposed to the website show “a new kind of prudishness”.
Mr Gatz said: “I am a proponent to talk openly about sexuality, without taboos.
“And that is exactly what this website does with explicit drawings.”
Sensoa spokesman Boris Cruyssaert said that the website is first and foremost meant for “youngsters older than 15”.
Mr Cruyssaert said: “But for youngsters aged ten or 11 there is not a single other website which so comprehensively gives answers.
“Then it is better that they go to allesoverseks.be.”