For Current Students -
Free Music Websites:
This is probably my favorite site for free music. It is very well organized by level and has recordings of the songs that you can listen to.
Great selection of songs grouped according to level. Each song has a recording and preview of the music, as well as a little bio of the composer for the classical songs.
Mayron Cole was a piano teacher in Houston who developed her own curriculum for teaching group piano. When she retired, she made all her piano method books available for free!
The music on this site isn't free, but if you sign up for their email list, they do email links to free music regularly. It is also a great site for buying sheet music written by current contemporary composers. You can listen and look at the music before purchasing.
This site has a lot of free music, especially classical songs. The pop songs listed are usually just the chords and small snippets, but gives you an idea of how to get started figuring it out on your own. (They can't print free modern pop music due to copyrights.) It also has a metronome setting and some background beats you can play along with and make up your own songs.
If you look past the clutter of ads on this site, it does have quite a bit of free music to print, arranged by how many years you've been playing. There are also some links to audio recordings to listen to, though they are not usually the same arrangement as the sheet music.
This site is best if you have a particular song you are looking for. Use the search feature, and it will probably have several versions to choose from.