What upper schools do the best job limiting cell phone use during the school day?

[Anonymous]

I wish that all schools -- nationwide (K to 12) -- would strictly prohibit cell phones. (As I understand it, in Europe and Asia, that is the case.)

I think that school should be a haven from the cell phone, and a place where kids think it's normal not to be starting at a small screen consuming videos or playing games.

In the U.S., the schools seem more lenient about cell phone use at school, in part perhaps because the parents do not strictly limit their kids' cell phone use, and therefore it would require the schools to hire a lot more staff just to ensure that the students are not on their cell phones.

Among private schools in the D.C. area, which school has the best policy on limiting cell phone use during the school day? 

(My nephew attended St. Andrew's, and I was impressed with their strict policy of no use during the school day (unless you were in the activities center). I hope that is still the policy, as our kids are in middle school and we are starting to look at upper schools.)


The idea for this thread stemmed from this thread about middle school
https://www.dcurbanmom.com/jforum/posts/list/1178674.page