SIL's Mission HR has a wealth of information about educating children on the mission field including a series of articles and links to other websites with information about choosing the right educational option for your child.
Interaction International offers an educational planning seminar in Wheaton, Illinois, to help guide parents through decisions about educational options for expats. The seminar covers many topics including educational options, second language issues, creating an educational plan, choosing homeschool curriculum, and preparing your children for transitions.
PACE, the Professional Association of Cross-Cultural Consultants in Education, offers an online course, Education Planning for Families in Transition, to prepare parents to deal with issues involved in educating their children overseas. They also have a blog with many helpful and informative posts.
Share Education Services provide support for parents who are educating their children in Europe and Asia. They offer assistance with choosing a schooling option and deciding what curriculum to use, support through transitions and in determining learning issues, resource help, and annual conferences.
Anchor Education, a British organization, offers educational counseling, workshops, conferences, and testing in Africa. They also provide booklets on gaining admission to UK universities while living overseas.
The Asia Education Resource Consortium is a membership-based organization assisting expatriate families living in Asia by providing conferences, testing, resource centers with lending libraries, and consultations to aid parents in choosing national schools or plan homeschooling.
ISMK's website provides an education resource which can be downloaded and contains information on educational planning and different options available to missionary families.