The Free Music Archive provides free, high-quality, music in a wide range of genres. The content on Free Music Archive is used under various creative commons licenses. The New York State Music Fund provided initial funding for FMA. FMA seeks to maintain a high-quality resource through the use of selected curators who approve or deny all submissions to the collection.

Anyone can download music from FMA for use in podcasts, videos, and other digital presentation formats. The music collections can be searched by genre or by curator.

Applications for EducationFMA could be a good resource for high school students looking for music tracks to use in podcasts and videos. There is an audio/visual/broadcast communications course taught at my school. FMA is the type of resource for which those students are often seeking.

I would be hesitant to use FMA in middle school or elementary school because of some of the language that students might find in some of the audio clips.
Here are some related resources that may be of interest to you:
Free Podcasting Solutions
Free Music and Pictures for Schools
The Oldies Come to Animoto’s Music Library