Every school can create their own policies and procedures. They can confiscate whatever is against the policy.
If it’s a mandated policy then the rule applies to the child of the board member and donor of the building the same as the “C” student and free tuition student. However, to arbitrarily pull over a bochur at random and require him to empty his pockets is wrong.
If there is suspicion of a rule violation at least TWO adults should witness the search of property. The adminstrator and a trusted staff person of the child in question who is currently on premises, or else contact the parents.
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.