Children in France will be banned from using mobile phones at school to in a bid to stop the spread of bullying, violence and pornography.

All junior and primary schools in the country have been hit with the new ban, which also covers tablets and smart watches, and begins today.

The new rule, which was a campaign pledge of President Emmanuel Macron, was brought in under a law passed in July.

High schools, which teach students aged 15 to 18, can introduce partial or total bans on electronic devices as they reopen after the summer break, though this will not be obligatory.

Proponents say the law, which has caused widespread controversy, will reduce distraction in the classroom, combat bullying, and encourage children to be more physically active during break time.

French President Emmanuel Macron made the ban on phones in schools a campaign pledge before his election in 2017

Marie-Caroline Madeleine, 41, said after dropping her daughter off for the first day of middle school in Paris: 'I think it's a good thing.

'It's a good signal that says "school is for studying", it's not about being on your phone.

'It's hard with adolescents, you can't control what they see and that's one of the things that worries me as a parent.'

Nearly 90 per cent of French 12 to 17-year-olds have a mobile phone, and supporters hope the ban will limit the spread of violent and pornographic content among children.

Education Minister Jean-Michel Blanquer has hailed the legislation as 'a law for the 21st century' that would improve discipline among France's 12 million pupils.

He said in June, as the bill was going through parliament: 'Being open to technologies of the future doesn't mean we have to accept all their uses.'

But critics dismissed the measure as a public relations exercise, and predicted it will be difficult to enforce.

The government has left schools to decide how to implement the new rules, recommending that they store students' phones in lockers during the day - but some schools do not have them.

French children under 15 will be banned from using mobile phones, tablets and smart watches at school under rules which begin from the start of the new term today (file photo)

Research shows that in French schools that have already banned phones, many pupils admit to breaking the rules.

Macron, a 40-year-old political centrist, pledged widespread reforms when he was elected in May last year, and education has been no exception.

Along with the mobile phone ban, he has halved primary school class sizes in disadvantaged areas to 12 in a bid to narrow a massive gap in grades between children from poor families and those from wealthy areas.

On the other end of the age spectrum, a shake-up of the higher education system to make university access more selective prompted a wave of student sit-ins this year.

Schools all over the world have struggled to adapt to the rise of the pocket-sized devices as parents grow increasingly anxious about the amount of time their children spend glued to the screen.

In 2015 New York Mayor Bill de Blasio lifted a ban on phones in his city's schools on security grounds, saying parents should be allowed to stay in touch with their children.