Banning baseball caps during tests was obvious–students were writing the answers under the brim. Then, schools started banning cell phones, realizing students could text message the answers to each other.

Now, schools across the country are targeting digital media players as a potential cheating device. Devices including iPods and Zunes can be hidden under clothing, with just an earbud and a wire snaking behind an ear and into a shirt collar to give them away, school officials say.