Are your students facebooking and shopping for shoes in class? Do they tell you that multitasking is possible because they are young and have neuroplasticity? Not so fast.
Take a look at some of the science behind why multitasking will affect your ability to learn and perform http://www.slate.com/articles/health_and_science/science/2013/05/multitasking_while_studying_divided_attention_and_technological_gadgets.html
You will have to read through to page 2 to get to the science, but essentially, multitasking in class hurts students ability to learn and perform in class and on tests. The article contains good advice for faculty. Show students this research, explain the effects of technology distraction while learning and ask that they put the tech away unless you are requiring them to use it. For students, use delayed gratification while studying. Go for 15 minutes without checking texts or social media. Allow your attention to be completely focused on the task at hand. As you practice this, you will find the time extends further out between technology breaks, even when you are using technology to study.