There are particular reasons by book writer services team that why technology and cell phones should be kept out of classroom.
Notifications will constantly be going off while you have your phone in your hands all day. Without even realizing it, you're driven to look. Likewise, students are distracted without even realizing it throughout the day.
What makes you believe kids won't do the same thing at home if they're always on their phones at school? Homework is less likely to be completed at home if distracted throughout the day and does not entirely work at school.
When a teacher is speaking to students, and many are on their phones, but only a few are trying to learn, the students on their phones are distracting the other pupils. Even if you don't have sound on, if you're playing a game or viewing a video on mute, someone else will most likely get a glimpse and be unable to look away. While you're on your phone, you're insulting your teacher, who is taking time out of their day to teach and assist you.
