I think it's mostly posturing. Mobile phones were already banned in class, and this was well enforced. But many kids, especially in cities, take public transportation to get to middle school. My experience with middle school in Paris is that it's also very unreliable schedule-wise. When school suddenly finishes 2 hours early, I appreciate getting a text message from my kid telling me what they're up to. It looks to me that it'll be hard to enforce reliably - are they going to search backpacks, and keep phones in lockers during the times kids are in school ?