I’m for the ban, and fully stand behind this Principal. My son’s Mesivta (not in Brooklyn, of course), has this policy, and the boys for the most part totally respect it. My son doesn’t even want to have a cellphone.
We all went to HS without them, and survived quite well. Aside from the access to the internet, and texting capabilities, I don’t like the fact that a lot of kids use texting to cheat on exams.
Generally speaking, I oppose bans, but this is perhaps the exception to the rule.