In Maryland in order for a school to call itself "Montessori" it has to be approved by some national Montessori association. The sole purpose of this seems to be to make money for national Montessori associations.
My daughter went to a Montessori school for pre-K. Based on my observations of the school it was great for pre-K and K, but awful above that. There were a lot of the same problems you describe. Half the kids seemed to have ADD and parents opposed to medication. Groups of kids tormenting others so that the class will consist only of their group. And teachers that just stand by and let this happen. And in my case, the owners of the school were complete idiots.
Still, for that year in pre-K my daughter got a great education.
Standards vary widely, in part because of the lack of trademark protection mentioned above. It's critically important to observe in person before sending your kids to any "Montessori" school.
We've sent our daughter to Montessori for a year and a bit, and it's been a joy to watch her blossom. We're moving soon, and keeping an eye out for a Montessori school that goes up to 6th grade.
I can't think of a more anti-Montessori environment than one where it's possible for a student to lie about daily activities. The central focus of a Montessori teacher is observing and directing students.