Students do have rights - and indeed also property rights - here. Of course, when in class the students could be asked to bring their phones to the front and be given them back afterwards, but without the law, the use of phones couldn't be restricted during breaks etc. Thus the new law which can make the restrictions even more severe during school hours.
Phone is a personal item. It doesn't disrupt anything by itself.
If a kid is using it during the class, then it is disrupting, but that can be dealt old-school way without the overall phone ban. If a kid starts stabbing others with a pencil, it will have to be dealt with, without the need for a pencil ban.
The phone disruption happens to the kids themselves and during the breaks (their free time).
Of course people have rights... the point is that schools seem not allowed to set their own rules.
The school my children went to in the UK has had a no phone policy for many years: phones must be off and kept in the pupils' bags. No need for a law change...
I think this is about approach to regulation and flexibility. In general being too restrictive about what is allowed makes things inflexible and poor at adapting.
Students don't have many rights when it comes to what you can bring to or do at school. We were prohibited from wearing certain styles of clothes, hats, couldn't even chew gum in class. Pretty much anything that could be called disruptive, damaging, or dangerous was banned. I'm not sure how phones ever were considered acceptable in the first place. Even in the pre-smartphone days, SMS was a huge distraction.