The Pilates Method Alliance (PMA for short) is an organization dedicated to protecting the public by establishing certification and education standards for Pilates Instructors.
The PMA is a not for profit organization and has campaigned over the years to provide a national certification. It is their belief that this will allow you the client to have confidence that your instructor has the basis of a good Pilates education.
The PMA wishes to protect the Pilates method. They do respect the various approaches to Pilates, but have an interest to keep the levels of education set to a high standard.
At present Pilates instructors can choose which certification program that they wish to take. It may be that one day they will have to take one of a few national exams. This would be a little like a personal trainer having a highly reputable certification such as NSCA, NASM or ACE.
At this time such certification programs such as Stott Pilates, Polstar, and the Physicalmind Institute offer a high standard of teaching. There are other schools and it takes some research on the part of the student to determine for him or herself which is appropriate.
You can also locate a Pilates instructor in your area who is registered with the PMA.