I'm thinking that they should be allowed in school, just not in the classroom. Exceptions only being once you've finished your required work (if you can work that fast). who knows? maybe listening to music could be an incentive to get people to work faster, and finish it to do what they want to do.
In my school it was we were allowed until last year. They said that they didnt want to take the responsiblity of all the electronic devices being stole so they banned mp3 players. Pesonally i prefered when music was allow not just because i could listen to awsome music but also because almost everyone was listening to stuff so i could actually concintrate in school and not be distracted by people talking. Lucky in my school no all teachers agreed with the board so in someclasses we still use them .
Kids will do better depending on what kind of music they listen to. If you're listening to your normal music, you'll actually get less work done, because you'll be concentrating on the music more than the work. If you listen to something without lyrics, and a light melody, it'll actually stimulate brain waves and make you work better.
Trust me, I did it as a home-based (A.K.A. non-graded and teacher had nothing to do with it) science experiment.
Mozart works best for math.