Please, please, PLEASE stay away from Casa de los Ninos Montessori School. While every school has their problems, I saw children being treated roughly during the six weeks I worked there. After seeing this two or three times, I packed my children up and walked off the job. I simply don't do that, otherwise.
I would advise looking at other Montessoris in the area, such as Blue Springs Children's House on 40 Highway. While there have been a couple of disgruntled employees, the parents and children seem to always be happy. Lakewood Montessori, right off of 291 in Lee's Summit is a larger school. Again, some disgruntled employees, but generally happy parents and children.
I, personally, plan on enrolling my son at Blue Springs Children's House in the summer or fall.