Here’s a story from Tarboro, North Carolina in which a 16-year-old student, Tilghmon Wayne Barber III used a key logger program to break into his teacher’s email and the school Moodle. The student allegedly used the admin Moodle access to change student profile pictures (not grades?!?).
Interesting story and more the reason to promote secure passwords and computer usage policies at your school. For more about Moodle security you might check out http://docs.moodle.org/22/en/Security