From
Microsoft itself:
"Qualified Educational User Eligibility
To license Office 2004 for Mac Student and Teacher Edition, you must be a Qualified Educational User or the parent or guardian of a Qualified Educational User who is a minor. Qualified Educational Users include:
* Full- or part-time students
* Home schooled students
* Full- or part-time faculty or staff of an accredited educational institution"
Edit: If it isn't obvious,
you qualify!