It is a question that keeps some parents awake at night. Should children be allowed to take mobile phones to school? Now economists claim to have an answer. For parents who want to boost their children’s academic prospects, it is no.

The effect of banning mobile phones from school premises adds up to the equivalent of an extra week’s schooling over a pupil’s academic year, according to research by Louis-Philippe Beland and Richard Murphy, published by the Centre for Economic Performance at the London School of Economics.

“Ill Communication: The Impact of Mobile Phones on Student Performance” found that after schools banned mobile phones, the test scores of students aged 16 improved by 6.4%. The economists reckon that this is the “equivalent of adding five days to the school year”.

The findings will feed into the ongoing debate about children’s access to mobile phones. In the UK, more than 90% of teenagers own a mobile phone; in the US, just under three quarters have one. The prevalence of the devices poses problems for head teachers, whose attitude towards the technology has hardened as it has become ubiquitous.

In a survey conducted in 2001, no school banned mobiles. By 2007, this had risen to 50%, and by 2012 some 98% of schools either did not allow phones on school premises or required them to be handed in at the beginning of the day.

However, some schools are starting to allow limited use of the devices. New York mayor Bill de Blasio has lifted a 10-year ban on phones on school premises, with the city’s chancellor of schools stating that it would reduce inequality.

This view is misguided, according to Beland and Murphy, who found that the ban produced improvements in test scores among students, with the lowest-achieving students gaining twice as much as average students. The ban had a greater positive impact on students with special education needs and those eligible for free school meals, while having no discernible effect on high achievers.

“We found that not only did student achievement improve, but also that low-achieving and low-income students gained the most. We found the impact of banning phones for these students was equivalent to an additional hour a week in school, or to increasing the school year by five days.

“Therefore, de Blasio’s lifting of the ban on mobile phones with a stated intention of reducing inequalities may in fact lead to the opposite. Allowing phones into schools will harm the lowest-achieving and low-income students the most.”

The research was carried out at Birmingham, London, Leicester and Manchester schools before and after bans were introduced. It factored in characteristics such as gender, eligibility for free school meals, special educational needs status and prior educational attainment. “Technological advancements are commonly viewed as increasing productivity,” the economists write. “Modern technology is used in the classroom to engage students and improve performance. There are, however, potential drawbacks as well, as they could lead to distractions.”