I've been doing my student teaching lately, and you guys need to understand how political and complicated schools have become. If you installed jammers in schools, not only would you have these whiny little bitches complaining that their rights have somehow been infringed, but you would have overprotected parents complaining that their children couldn't call them in an emergency.
I fully support banning all cell phones from use on school grounds during school hours. I'm reasonable, I think students should be able to use them before their first class, during lunch hours, and after school on school property. Other than that, detention for anyone seen using them.
I'm not strict about much. I do think students should stay on campus during lunch break (it's a public safety and revenue stream thing) but should provide plenty of on-campus dining options (when I went to school, your choices were pizza or burgers. And we wonder why our kids are so fat ...)
People need to realize that schools are not just learning installations. They're much more than that. They're a key point in socialization and cultural integration for young people. They're a crime deterrent. They're a day care. In fact, I would put "education" somewhere in the middle of the functions of a public school system.