There seems to be some armchair lawyers out there interpreting the license agreement for Google Earth to mean you can’t use Google Earth for education. To dispel this myth, OgleEarth points out that the Google Earth Help Center specifically states that it is fine for you to use Google Earth in education:
Can Google Earth be used in an educational setting?
The use of Google Earth for educational purposes in primary, secondary, and post-secondary institutions is OK.
In fact, Google has been known to give away Google Earth licenses to educational institutions, and included both Google Earth and SketchUp software for free in a large educational program for the state of Maine a month ago.