How does it work today?

Like a lot of conventions and philosophies that originate in another century it's natural to look at their relevance today. There's more than one book about Montessori's use in present day -mostly by proponents of the cause themselves. Yet they're not without an unarguable ,if a bit fluffy , logic.
It goes right back to the founder though- Montessori herself was a scientisit. And it shows.

People don't essentially change over a hundred years. Sure, our physical circumstances have changed vastly but sociologically and politically we still have the same needs and wants.
Montessori was a peace activist of sorts. She campaigned for world peace as part of her general philosophy; children being the key holders to it's future . Hence it's a subject discussed daily at Montessori schools which of course incorporates a worldwide awareness into the mind of each student at primary level.

Perhaps a question more relevant than where Montessori belongs today is how is it monitored and controlled.
Because in the USA alone there are more than 8000 schools bearing the philosophy's name, they have their own organisation governing teaching , training , oversight of equipment production and the upholding of the Montessori name. For the rest of the world the Association Montessori Internationale does this job.
The only problem is that the standard is still difficult to control entirely because the Montessori name and philosophy is not trademarked, nor owned by any one body worldwide.
As one of Maria's grandchildren points out ,the name can be used by anyone wishing to incorporate the pedagogy into their teaching and therefore is easily misused or misinterpreted reguclarly.

Therefore as parents , advise is regularly given to check individual schools outvery carefully on their own merits rather than simply trusting the affiliate Montessori name.