2nd type - the group they rarely put out their phones. These students are the student have more attention thus learn the material. In the past, I had only 1 or 2 students per class who really had a problem with time on task. Today, with cell phone usage for students is more than tripled from my humble observation. This had lead to the decline of students scores overall.
Maybe read this --> http://blogs.kqed.org/mindshift/2013/12/age-of-distraction-why-its-crucial-for-students-to-learn-to-focus/?utm_content=socialflow&utm_campaign=nprfacebook&utm_source=npr&utm_medium=facebook