I’m guessing its meant for the devices thats already installed in class or belong to the school, so it gives them time to change or remove it.

They’ve been “confiscated” at the beginning of every school day and put into this case with a bunch of pouches for phones since cell phones became a thing in South Korea, but apparently this was a decision left up to the school principal. The last middle school I worked at didn’t allow students to bring phones to school at all. I’ve never heard of any schools that allow phones in class outside of some supervised activities where they might need it. I guess this law just makes the rule mandatory for all schools.