Is a teacher allowed to take one of your items and not return it until the next day?

The answer to
your question has not actually been reviewed by the Supreme Court, but is largely held by a
decision made in Arkansas called Koch v. Adams.  In the case a young man
had his phone seized for two weeks where in the school refused to give him the SIM card.
 

The student sued the school claiming that the confiscation violated his
rights and at the very least they should have given him the SIM card to protect his right to
privacy.  

The ruling enforced the importance of school documentation and
maintaining a paper trail. Because the school had a clear policy that had been explained to the
student and the student's parents; because the student had signed a contract specifically
outlining the consequences of phone usage at the school; and because the school did not search
the student's phone, the school's right was upheld to follow policy and confiscate the phone
according to the rules set by the school.  

Because of this particular
ruling, schools are responsible for informing students and parents of the rules, keeping
documentation of warnings and parent conferences that try to solve the problem, and their
reasoning for the confiscation.  If they follow these guidelines, they can keep the items for as
long as the consequence policy stipulates.