LONDON-It pays to put your phone away during class, a new study has found.

Researchers at the University of Rutgers conducted an in-class experiment where students divided their attention between phones and lectures.

They found that using electronic devices during a lecture can shave 5%, or half a grade, off of undergraduates’ marks in their end-of-term exams.

The study shows for the first time that using a phone in the classroom primarily impacts long-term retention, researchers said.  For the study, 118 cognitive psychology students at Rutgers University took part in the experiment.

Phones, tablets and laptops were allowed in one-half of the lectures and banned in the other half.

Students were taught the same class material by the same instructor over roughly the same amount of time, according to the study, which was published in the journal Educational Psychology.

Using a phone in class didn’t lower students’ scores in comprehension tests, but it did effect their long-term comprehension and retention of class material.

Interestingly, they also found that when electronic devices were allowed in class, students who didn’t use them still did poorly, suggesting that technology use ‘damages the group learning environment.’

‘These findings should alert the many dedicated students and instructors that dividing attention is having an insidious effect that is impairing their exam performance and final grade,’ said Arnold Glass, who led the study, in a statement.

‘To help manage the use of devices in the classroom, teachers should explain to students the damaging effect of distractions on retention - not only for themselves, but for the whole class.’

The study also illustrates the impact of divided attention in the classroom, or that if someone is forced to segment their attention between two tasks, they’re less likely to be able to recall vital information later on.

In the course used in the study, students were given in-class questions to help them remember material, aside from just passive listening.

This means that students could do worse in other courses, based on how they’re taught, if they’re given access to electronics during the lecture.

The impacts might be shown in more than just the end-of-term exams, in things like unit exams, too.   

Glass told ABC News that the study’s findings are applicable to not just college lectures, but also high school and middle school classes, as well as meetings.