(Edit: obviously will need some accommodations for disabled students, and computer labs will have to exist for technical literacy classes.)
But I wouldn't oppose banning those as long as the schools provided an AlphaSmart (because again, I'm really bad at handwriting). I think e-readers would be best but those are expensive.
I think banning tools for teachers, like projectors, is unnecessary. I suspect I learned easier from projected computer screens vs. staring at a whiteboard, but anything projected on the screen (e.g. powerpoint presentations) could be passed to students on paper, except movies but those may rarely be necessary.
I'm fairly certain schools had projectors a few decades ago, and nothing bad came of it.
You don't really need to ban phones from schools; just ban them in class. I don't know why this stuff is treated as such a big deal. Students should pay attention in class, which means not using anything (not devices, paper, books, etc.) except as needed for instruction.
None of these tools is designed for the sole purpose of interacting with random people on the internet.
A child can get all the potential benefits of a phone from books, radio, film, television and game consoles — all the while not interacting with random people on the internet.