Sex education lessons in schools will now cover topics including sexting, female genital mutilation and healthy relationships.
The Department for Education issued new guidelines for teaching sex and health education as part of a new curriculum for primary and secondary schools.
Pupils as young as four will be taught about relationships and internet safety, along with new lessons teaching the link between physical and mental health, the importance of getting enough sleep, the dangers of sexting, and how to spot anxiety in their friends.
A new curriculum will come into force in 2020 and will include three new subjects: relationships education from primary school, relationships and sex education at secondary school, and health education for all ages.
It will be up to teachers to decide the frequency of lessons.
Primary school pupils will learnt what to do if they come across something online that makes them uncomfortable, and how to deal with trolling.
Secondary school pupils will be taught about female genital mutilation (FGM) – focusing on awareness, the availability of support networks, and reminding them that it is illegal.
Students aged 11 and older will be taught about honour-based abuse, as well as grooming, forced marriage and domestic abuse.
Education Secretary Damian Hinds said: “Growing up and adolescence are hard enough, but the internet and social media add new pressures that just weren’t there even one generation ago.
“So many things about the way people interact have changed, and this new world, seamless between online and offline, can be difficult to navigate.
“Almost 20 years on from the last time guidance on sex education was updated, there is a lot to catch up on.”
This afternoon MPs will debate whether parents should be allowed to remove their children from sex education lessons when the new guidelines kick in.
More than 100,000 people signed a petition demanding the right to take children out of the new classes.
Dr Katherine Sarah Godfrey-Faussett, who began the petition, said: “We have grave concerns about the physical, psychological and spiritual implications of teaching children about certain sexual and relational concepts proposed in RSE (relationship and sex education) and believe that they have no place within a mandatory school curriculum.
“We believe the above factors have not been given enough consideration and that many of the RSE resources being produced by lobby groups and external organisations will actually cause more harm than good, particularly when child development and psychological factors are considered.”
Speaking on ITV’s Good Morning Britain on Monday, Education Secretary Damian Hinds said that primary school pupils will be taught about ‘respectful relationships’.
When asked if this included teaching children as young as four or five about gay and transgender relationships, he said this would not happen.
Mr Hinds said: “When you start to talk about different adult relationships, that has to be done in an appropriate way. It is not about saying this stuff all happens at the age of five.
“At a young age, what we are talking about is having respect for all kinds of people. You have to have respect for all the different families you come into contact with.
“Nobody is suggesting that there should be these difficult conversations with children at that age, but relationships in the broader sense, friendships, interactions and how you interact with other children and adults. That’s very important from a very young age.”