Part of the problem is with each step down the ladder there's less authority and support and more chances for blowback from angry parents going higher up the chain. Teachers fear not getting support from principals if they're DIYing a device ban, principals fear blowback from complaints to the board or superintendent etc.

There's also the normalization problem at the teacher level where kids are used to using them in other classes so it's a bigger lift to get different behavior in one specific class.