Saw a TV interview with a high school teacher who was happy that Los Angeles County is going to install "physical barriers" to cell phone use by students. As I wondered what sort of physical barrier would be practical, she repeated that phrase a few times but never explained it. Since she did not anticipate that listeners would be puzzled, I was left thinking she must not be a very good teacher. I can't imagine LA putting Faraday cages around all the schools. LA schools might already have metal detectors, so that's probably not the new physical barrier. Any idea what will be implemented?