that is an often repeated claim that has not been verified. it could be a selection effect, or it could be that it actually works. montessori was originally developed for handicapped children, that is precisely the kind of children that struggle in a traditional classroom setting. in india montessori is used in public schools.

i have seen it work in china, and i can tell you that chinese kids are not angels, no matter how wealthy the parents are. actually the more wealthy the more likely those kids are misbehaved because those parents come in with a lot of entitlement that their children inherit.

furthermore the name montessori is not protected, so there are a lot of fake schools out there. therefore i suggest you look at the actual method and reason through the claims of why it is working.

the magic way that you are looking for is to give each child individual attention and then let them work by themselves. kids are disruptive most often because they are bored. children in a montessori class are never bored because they can choose themselves what to work on. that montessori works can therefore be reasoned from first principles. it does what everyone recommends: give more attention to children, and give them work that they are actually interested in.

if you object to that then i'd request that you provide actual evidence of the method failing instead of repeating claims without substantiating them.