We studied mobile phone bans in England, as mobile phones are very popular there amongst teenagers. The research involved surveying schools in four cities in England (Birmingham, London, Leicester and Manchester) about their mobile phone policies since 2001 and combining it with student achievement data from externally marked national exams.
After schools banned mobile phones, test scores of students aged 16 increased by 6.4% of a standard deviation, which means that it added the equivalent of five days to the school year.
While our study was based in the UK, where, by 2012, 90.3% of teenagers owned a mobile phone, these results are likely to be significant even here in the US, where 73% of teenagers own a mobile phone.
It is important to note that these gains are prominent amongst the lowest achievers, and changing policy to allow phones in schools has the potential to exacerbate learning inequalities.