Files Types for music

For AP exams the kids were using GarageBand to record their music files, and the files saved as .M4a and the required AP format was to be .Mp3.  iTunes is suppose to be able to convert the files easily but I had no luck.  I was however able to use a VLC player to convert the files to an .Mp3.  Here is a I handy tool I found on the Dummies site:

File Type	Compressed?	What’s It Good For?
AIF	No	Audio CDs, iTunes, and archiving music in the file format that retains the most audio information. Can be used with iPod, but files are 5–10 times the size of compressed formats.
WAV	No	The equivalent of an uncompressed AIF file on a Mac, this format is used for sharing files with Windows users. File sizes are 5–10 times the size of MP3 files, which is the compressed file format of choice among Windows users.
Apple lossless	No	iTunes and archiving music in the file format that retains the most audio information. Can be used with iPod but files are 3–7 times the size of compressed formats.
MP3	Yes	iTunes, e-mail, the Web, and sharing with Windows users. Files are much smaller than either uncompressed format, making MP3s ideal for iPods.
AAC	Yes	Same as MP3 but is Mac-only. Slightly smaller files than MP3 and slightly better sound quality in those slightly smaller files. Most Windows users can’t use AAC files.