Are students really allowed to be on their phones during class at a lot of schools?

When I was in high school, we didn't have smartphones, but we had game boys, flip phones, and graphing calculators that could play games.

If we were ever caught playing with any of these things we got in trouble. That seemed sufficient at the time, but is that not the case anymore?

iPads are required in some public school classrooms, in place of textbooks! There no "lockdown mode" that the teacher can enable, to lock to the apps/websites related to the lesson. It's INSANE.