The crucible happened six years ago: 2012 was the year teen mobile phone ownership crossed the 50 per cent mark.

Since then, the saturation of these hand held devices has only increased, nine out of 10 teenagers have their own mobile while 73 per cent have a smartphone and the majority of these kids would feel they were missing a limb if they had to come to school without it.

Despite this proliferation of phones and the warnings associated with them, education authorities across the world still haven’t worked out what's the best thing to do with these instruments of mass distraction.

Most teachers are acutely aware of the disruption one mobile phone can cause to a working classroom.

The ping of a single text message can cause everyone who was previously focused on the lesson to stop what they are doing, even involuntarily, for a moment and think about their own device.

The pupils will know the text is not for them but the noise will remind them about their phone nestling in their pocket or school bag and they will want to check it, experiencing that addictive fear of being disconnected from the group.

It will take a little while for the class teacher to get the pupils to focus again on their work.

This interruption to learning might only last for a few minutes but all of these minutes add up.

A recent study by the London School of Economics found that in schools where mobiles were banned, test scores of 16-year-olds improved by over five per cent; the equivalent of adding an extra working week to the school year, the researchers calculated.

Furthermore, this study, conducted in more than 90 UK schools, revealed that a phone ban helped both teenagers from poorer backgrounds and those who were not achieving academically.

This cohort  improved by twice as much as their more academic or wealthier peers.

Last year the French Government took a radical step when they announced a total ban on mobile phones in schools, extending from an original ban where mobiles were not allowed in the classroom to phones being also prohibited during breaks and lunchtime.

In theory the ban sounds straightforward but in implementation might be more complex as the French authorities still haven’t worked out what happens to any phones brought into schools and whether teachers will be able to search pupils’ bags or pockets for offending telecommunication devices.

Yet the lack of clarity about what to do about mobile phones was highlighted when just as the French Government were taking a decisive step in one direction, the mayor of New York City decided to lift a 10-year-long ban on phones that had been imposed in the city’s schools.

The mayor, Bill de Blasio, reasoned that the ban was discriminatory. It stopped parents being in contact with their children during the school day, which could be crucial in a chaotic household, as well as only being properly enforced in schools which had metal detectors; generally installed in schools in areas of deprivation.

This lack of universal consistency over what to do about mobile phones is mirrored in individual schools in Australia and the UK, where neither country has a countrywide policy.

In some schools where there are a lack of computers, the use of them is actively encouraged.

Teachers argue that rather than pupils being unable to research topics online or do calculations, it would be crazy to ignore the computers in their pocket.

Similarly, rather than students laboriously recording material from the whiteboard into their notebooks, it would seem obvious to use the device which can photograph the information immediately.

But for me, this educational usage assumes pupils will act responsibly, and this is a heavy assumption to make.

If a pupil is filming an assessment what if they decide to film the girl they like in the class or the teacher making a mistake or a fight breaking out?

And what happens when a pupil is carrying out research on their phone when a message alert comes on screen?

I think the child would have to have the willpower of a saint not to have a look to see who has messaged them.

Furthermore if a school assumes everyone has a phone to support their studies, this assumption puts a pressure on the have-nots, whose parents might only be able to afford a simple pay as you go phone or, horror of horrors, have no phone at all.

But it is not only the negative effects on concentration where schools should be alert to the use of mobile phones, it is also how they affect the students' mental wellbeing.

Psychologists from San Diego State University looked at the prevalence of mobile phone use amongst teens and depression levels in the United States.

Professor of psychology Jean Twenge, who led the research and has written i-Gen, found a link between a massive spike in depression levels in American teens and their increased use of mobile phones.

Not only did the number of US teenagers who experienced the classic symptoms of depression, feeling useless and joyless, rise by a third between 2010 and 2015, but 23 per cent had attempted suicide.

Twenge's correlation is compelling; as teenagers walk to school, spend their break and lunchtime then return home with their phones glued to their thumbs, their opportunities for social contact are greatly reduced.

As face-to-face interaction between friends falls, levels of depression increase.

This research surely supports schools everywhere following France’s lead an implementing an outright ban on mobile phones, not only to support the mental health of our pupils, but to remove a major source of classroom bullying.

Any attempt to end the use of mobile phones in schools could only proceed with the backing of parents and carers and schools would initially need to be quite strict initially in implementing the change, however pupils should be able to adapt to life without their phones, at least for part of their day.