Choosing a school for your child is never a difficult task. What will they respond well to? What teaching method is best? Before making a decision, look into the best Montessori schools and what they have to offer.
The Montessori system was created by Maria Montessori. She valued the choice of the children.
She believed that children know what they want and should do, and should have the ability to choose their activities. The classrooms are divided for ages 3-6, then 6-9, and then 9-12-year-olds. Having an age mix allows the children to grow up and become leaders as they age through the classrooms.
The philosophy is that the instructor is not the only one in charge. This whole class will be running the environment. There are no tests, exams, or grades. Even with older ages, it is not believed that tests are in any way helpful. They only highlight what you do not know. The teacher should be supporting the children to find out what they do know.
If they enjoy learning at private schools, they will be able to adapt quickly to a new environment. Treating education and work positively is how Montessori best prepares children for their future.