My kids were basically required to have a phone for school. In theory they could use a laptop for everything but in practice it was assumed you had a phone.

They were supposed to use the calendar for assignments (and were given time to use the calendar), the teacher would tell them to take a picture of the white board with their homework assignment on it, and they used some private app (don't know the name of it) for messaging the teacher.

This was a few years ago though, so maybe now the tide has turned?

Edit: The rules have changed:

https://tea.texas.gov/taa-letters/implementation-texas-house...

that would be illegal right now, kid/parents can call police you stole their phone and you would be in trouble with police, any school rule isn't above the law, which is why there must be confiscation option clearly mentioned in the smartphone ban law