Typical prohibitionist mindset. Lots of people use X, we don't like X, we ban X instead of understanding how to properly and moderately integrate X into our lives. Smartphones and tablets are GREAT learning devices. If we keep blaming the ineptitude of teachers on devices the quality of education will never progress.

EDIT: part of the education process is to teach kids how to use and not abuse these devices and when it's appropriate to use them for entertainment. Telling them "you can play Fortnite for an hour after you finish this math challenge" is way better than "you can't play Fornite at school!". I remember having the same policy applied for when I was in school and we would play Pokemon TCG. When it was banned we would play in secrecy during class, when they gave up and allowed us to play during recess we stopped playing during class. It's just common sense.