Association Montessori International/USA (AMI/USA) offers training to be a Montessori teacher. You can simultaneously earn a Master's degree and an internationally recognized AMI certification to teach in Montessori schools in over 110 countries around the world. AMI is the organization originally founded by Dr. Maria Montessori in 1929 — particularly to safeguard her developed methods and training standards for Montessori education.
www.ami.edu/usa

"Montessori is a brain-based developmental education method that allows children to make creative choices in how they discover the people, places and knowledge of the world. It emphasizes hands-on learning, self-expression and collaborative play in a beautifully crafted environment of respect, peace and joy."
-Steven Hughes, Ph.D., L.P., pediatric neuropsychologist