Are your staff fully certified?
There are no state regulations on the certification of private school teaching staff, Montessori or not. I have observed many “upscale” private schools that do not have one person on their staff with a degree in education, or anything form of certification. I once visited a school where the only person who had a high school diploma was an aide!
The “accountability” movement is interesting. Public schools are mandated to have “highly qualified teachers” private schools - who knows? Their whole staff could be Ph. Ds or they all could be mothers who want a cut in tuition for their child.
Therefore, it's important to ask of any Montessori school:
• What kind of education do your teachers have?
• What kind of certifications do they have?
• How do they keep apprised of new educational findings and techniques?
A school worth its money will have a certified owner, director, principal, and head teachers. Having Montessori certified aides, and specialty staff is wonderful, but not needed.
By the way, don’t accept the word “trained”. If you are told, “We have a fully trained staff”, repeat your question: "Are your staff members certified and with which specific program?" Training can mean anything from actually getting a degree to having read a web page.
As a personal anecdote, I once knew a director/owner who told people she was “Austrian trained”. She just seemed to forget to tell people that her “training” was in hotel management! More than that, she had failed all her classes her first year and dropped out! Her extent of Montessori knowledge came from reading one web page. Not even a site, just one page prior to opening her school.