Smartphones can be harmful to children in many ways, but perhaps one of the biggest threats of mobile devices is the negative impact they have in the classroom.

A new study co-authored by University of Texas-Austin economist Richard Murphy reveals that prohibiting cell phones in school can have the same affect as extending the academic year by a week. While technologies are often celebrated for creating new ways to learn in a school setting, Murphy says that they can also backfire.

"New technologies are typically thought of as improving productivity, however this is not always the case," Murphy, an assistant professor of economics, said in a press release. "When technology is multipurpose, such as cell phones, it can be both distracting and disruptive."

Murphy and Louisiana State University professor Louis-Philippe Beland came to this conclusion after reviewing student exam records and mobile phone policies from over the span of 12 years, noting the changes in performance before and after schools enforced cell phone restrictions. The researchers looked at 91 schools in England from 2001 to 2013.

Who gets the most out of cell phone bans?

The researchers saw test score improvement in classrooms that forbade cell phones, particularly among low-achieving students. The cell phone ban also had a greater positive impact on special needs kids and those who are eligible for free meals. The researchers found that the best performing kids were the least impacted by cell phone restrictions, leading the authors to believe that low-income and low-achieving students could benefit the most from cell phone bans in schools.

"This means allowing phones into schools would be the most damaging to low-achieving and low-income students, exacerbating any existing learning inequalities," Murphy said. "Whilst we cannot test the reason why directly, it is indicative that these students are distracted by the presence of phones, and high-ability students are able to concentrate. Banning cell phones in schools would be a low-cost way for schools to reduce educational inequality."

Smartphones perpetuate cheating in school.

Smartphones can also be a powerful tool for kids to cheat on tests. Using smartphones, students have been known to take pictures of exams and go online during the tests to look up answers to questions.

After two Maryland students posted test questions on Twitter in March, Cheryl Bost, Vice President of the Maryland State Education Association, said smartphones in the classroom are a growing concern among educators.

"Teachers have been concerned with students having their own devices in the classroom even during regular class time and what's being recorded, what's being taken pictures of and things like that," Bost said.

In 2010, reading and language arts teacher Culham Amengor told the Sun-Sentinel that instructors know to watch students closely when taking exams.

"These kids are very fast and very sharp. They have the technology in school and they know how to use it."