Psi-IM - Psi-IM is a messaging program that is designed for the XMPP network.
PowerSchool - PowerSchool provides a K-12 education technology platform for operations, classroom, student growth, and family engagement.
Gajim - Full featured and easy to use Jabber client
Clever - syncing between education applications for K-12 schools
Empathy - Apps/Empathy - GNOME Wiki!
Claroline - Claroline is a collaborative eLearning and eWorking platform.