The Foundation for American Christian Education (FACE) is the largest organization in BPA. Originally in California, they moved to the east coast. Visit their About Us page here. They are the publisher of the Red Books, the Noah Plan and hundreds of other materials. (They have trademarked the phrase Principle Approach.) They are an invaluable resource for Christian history and home education the BPA way.
The Commonwealth is an online community that members can use to connect with other members, to access material from FACE and to interact with FACE staff.
Please visit their site for info on everything BPA. They offer many articles and materials that will help you on your way.