Exclusive: All schools to teach sex and relationship education from age four

It is a question that's long been asked in our schools: Who tells children about sex and relationships - parents, or teachers?

Except the answer these days, is that it's often the internet.

And over recent years there has been growing concern that the answers provided by search engines and websites aren't the lessons children should be learning.

I understand that on Tuesday the Government will try to address this new reality by completely revolutionising the education schools provide, bringing forward legislation that will ensure every child from the age of four is taught about safe and healthy relationships, and later, about sex too.

Currently the system is complex and dependent on the type of school a child attends.

Sex education is only compulsory in schools run by local authorities, and even then the curriculum is limited to the basics of biology.

There is guidance for schools which wish to go further, but it hasn't been updated since 2000 - long before children could pull out their smart phone after class and get their own education.

• Pupils speak positively about sex education

Now the Government is pledging to bring in new "Relationship and Sex Education" to every primary and secondary school in England, including academies, independents and (most controversially) even religious free schools.

The exact curriculum hasn't been laid out, but I understand the lessons would be age-appropriate and are likely to focus on issues such as staying safe online, "sexting" and abusive relationships.

Crucially, parents would not be able to withdraw their children from the relationship classes, although they could still withdraw them from the biology lessons, as is currently the case.

Last week, I visited Whitefield School in London to see what these lessons might look like.

The teachers there bring in the education charity Tender to give children workshops on healthy relationships, with pupils able to discuss their own concerns through drama and group exercises.

Incredibly, within fifteen minutes of the class, several pupils had already raised the issue of sexting.

Others were concerned about abusive relationships.

Age 13-15, the children were already acutely aware of the pressures of social media and the dangers they face.

Every one of them told me the class had been helpful and that other children should get the same education.

• Headteacher believes sex education move is important

Indeed, surveys suggest the vast majority of children - and parents - are in favour of such lessons.

But there is likely to be strong opposition from religious groups and those who insist parents should always be the first authority on personal matters.

But many MPs, charities like Barnardo’s and even the Girl Guides have long been arguing that the internet challenges that parental authority, with children exposed to online pornography and other graphic content from a young age.

It would appear that the Government agrees, and it will now be down to teachers to try and correct the lessons of a digital age.