In the US about 75% of all children have a cellphone; in Britain the figure is closer to 90%. Recent research by the London School of Economics found that in schools that banned phones, test scores improved by 6%. Banning phones had the most positive impact on low-achieving pupils and those from low-income families: for them, it was equivalent to having an extra hour of teaching a week. However, it had no discernible effect on high achievers, less easily distracted by phones. Most British schools ban mobile phones, but in the US, bans are now being gradually lifted.

It is right to ban phones in the classroom, and they should be temporarily impounded if used. But the real reason for children having phones is so that they can contact their mothers, often late or unable to collect their kids after school, and reassure them that they are safely on their way home. Some parts of the media seem to base their whole business plans on stoking up fear of child murders, abductions and abuse. In the old days children walked home from school and no one thought twice about it. Now it is a different matter. Recently, near Washington DC, the police picked up two children walking home from school, arrested them, took them into care and are threatening to take the parents (both, incidentally with PhDs) to Court for being irresponsible parents, or some such stupid nonsense. Civilisation may not be in decline, and the crime figures are indeed lower, but fear is, without doubt, more prevalent, a very un-Epicurean emotion.