Simple solution: Kids keep their phones on them as they please but using them in class is a no-no. What's so hard about that? Oh, wait, I know, people over 18 years old have forgotten how to be adults these days and stay in control of the situation.
Yeah you're right. All of these "zero tolerance" school rules are merely the result of laziness and incompetence on the part of the teachers. It takes too much time and judgement to weigh every instance on a case by case basis so they just implement a blanket policy.
This kid needs love and support during such a stressful time in his life. Instead he is looked upon by the faculty as a problem to get rid of.