I was asked recently about downloading music from the internet for school projects. My answer is as follows...
Although you can download music from the internet for school projects you shouldn't unless it is copyright free music or licensed under Creative Commons and labelled for re-use.
Asking creators of the audio can be time consuming and you may well be declined.
Most commercial music from well known musicians has been copyrighted and should not be used.
'It allows a teacher to play a sound recording in a school, for instructional purposes, provided that the audience consists only of teachers, students and others directly associated with the activities of the school.'
Works licensed under Creative Commons are often free to be used and remixed as long as you give attribution to the creator.
Here is an explanation of Creative Commons
https://creativecommons.org/ and here is a video to help explain
Another good option is for children to make their own music with tools like Garageband on an Apple, Audacity on a PC or Aviary on the web.
http://www.aviary.com/tools/music-creator
There are a number of websites where you can search for and download Creative Commons Music.
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Here is a list of some of them https://creativecommons.org/legalmusicforvideos
Soundcloud also has creative commons music
http://soundcloud.com/creativecommons Search for FREE
Dig CCMixter is another good site for podsafe music with work from original artists