The Montessori Foundation and its member organization, The International Montessori Council (IMC) are non-profit organizations dedicated to the advancement of Montessori education in the US and abroad. This website provides answers to frequently asked questions. They have an online library of articles for parents and publish 'Tomorrow's Child' Magazine.
The American Montessori Society was founded in the late 1960's by Nancy McCormick Rambusch, an AMI Montessori trained teacher. In AMS schools, teachers continue the methods developed by Dr. Montessori while bringing in outside resources, materials, and ideas to extend or supplement the Montessori curriculum. Wilson Montessori is an AMS associate school. The AMS website has a lot of resources for parents:
AMI was founded in 1927 and is headquartered in Amsterdam, The Netherlands. In AMI schools the Montessori method is used precisely in the manner prescribed by Dr. Montessori without any deviation or extensions.
Friends of Montessori is a non-profit organization that supports public Montessori schools in Houston ISD.