Student planners are paper calendars and to do lists. One can have these things without a CPU, RAM, and a network connection.

Can we be sure it's social media at all? Or is it a behavior issue? Does it matter if they are watching tiktok or mucking with a calendar if they aren't participating in class?

Enforcement will likely come down to don't do stupid shit with your phone or risk losing it. Ignoring class for a phone is stupid shit regardless of what's on the screen.

I think you underestimate how attractive socializing with your friends is. My niece's school uses chromebooks and they spend a lot of time using google chat with eachother during class.

There are enough offline alternative for that, including paper based. Although I keep telling her it can't possibly be good in the long term for her skin, my eldest daughter keeps writing her homework tasks on her skin.

You're describing the improper use of any tool. I would have liked to bring a penknife to school to sharpen pencils, but it's probably good that they were banned.

A smartphone isn’t just a calendar and todo list. I don’t think even blocking just social media is enough in schools as the devices offer plenty of other distractions.