“There are laws in America that must be followed or the school and the administration could find themselves in a world of trouble. The church/state argument will not trump the legal issues in this case.”
The laws in America as they pertain to search and seizure of students in school are not much of a concern here. First, students in American public schools have very little in the way of 4th amendment rights, as the Supreme Court has held that the students rights to be free from unreasonable search and seizure are balanced by the school’s educational purpose and need to maintain order within the school. In short, from a legal standpoint, students have very little in the way of rights. Its even less of a concern with respect to a private school like a Yeshiva, which is not a state actor, and therefore not subject to the dictates of the 4th amendment. When you sign up to go to a private school like a Yeshiva, you’re essenntially signing up and consenting to their way of doing things.
As for the actual question, of course the principal should enforce his policy. Also, of course, he should not enforce it in a way that is demeaning to students, but students generally invite that sort of thing by trying to get around the policy. Its not clear if the policy being asked about it along the lines of cellphones are evil and should not be in this Yeshiva because they lead people to going OTD, or cellphones are disruptive and distracting to learning, so they should not be in this Yeshiva. Not that it really matters, students should follow the rules.