Noteflight is an excellent site w/ educational portal (COPPA compliant) that allows users to create and share music right in their browser. This is an excellent resource for Music teachers looking to teach music notation and create online assignments in a safe environment.
I highly recommend checking out Noteflight by clicking here!!!
For a more detailed review check out Graphite.
Below is a brief demo video...
For my Pinterest board on Web 2.0 for Schools click here.