I think people who do sports with their dogs are likely to be able to see these preferences easier. I do agility with mine and there’s a lot of time spent watching their feet and seeing where and how they start and land jumps and such. He tends to favor his left and will typically lead with it. When we’re doing scentwork he also raises his left paw to signal as well. He uses both paws for all sorts of things, but I believe he does favor his left!
As an elder millennial I struggle to see the problem honestly. When cell phones first came out and teenagers started getting them when I was in high school, the policy was you could have the phone in your bag, but if the teacher saw it during class they would take it away and your parents would have to come get it at the end of the day.
I am not sure when schools started allowing phones to be a free for all, but going back to the original phone rules I had seems like the easiest solution no? Kids still have the phones in case of emergency, but they cannot use them during class. Is the concern about the confrontation of taking the phone from the kids? That’s the only argument I can see, but if they resist, send them out! I’m genuinely confused here.