I've seen a few questions like this one on this site, however, I have not been able to find a credible source dictating what gives schools the power to confiscate a device?
Let me give an example:
Bob goes to a public school in the United States. Bob's school has a policy that allows the school to confiscate Bob's phone if he does not use for "educational purposes" or misuses it during class. At the beginning of the year, the school sends out a document where Bob and his parent/guardian are supposed to place their initials which means they agree to the handbook. Bob and his parent/guardian return the document, however, do not sign/agree to the handbook. What gives the school the right to legally confiscate Bobs phone without his consent? (Please be specific)