Every year thousands of Montessori parents approach their children's school, or are themselves approached, about the possibility of taking Montessori teacher training. A substantial number of Montessori teachers and administrators began as Montessori parents. Montessori teacher training is available from several dozen centers and institutes across America and Canada. For the internationally minded, courses are available in many other countries as well. Courses usually involve a year of study.
Some courses run during the school year.
There are dozens of different Montessori societies and centers offering training. The quality can vary from mediocre to superb. One basic consideration is the credibility of the diploma received upon completion. You should be aware that some Montessori schools will require teachers to hold one or the other of these two credentials. Courses accredited by the AMS are often organized along the lines of a one or two summer-long institute followed by a year of supervised student teaching.