"Parents sending their children to a Montessori school may be more engaged in their education, so their own educative style at home may positively influence their success," explains Javier Bernacer at the Institute for Culture and Society, University of Navarra in Spain.
Unfortunately, it is very hard to apply the same rigour to the testing of educational interventions. You might decide to compare pupils in Montessori schools to those in some other educational system. But many Montessori schools are fee-paying, and the parents' choice may be related to many other confounding factors that could also influence a child's progress. It's not just the parents' wealth that matters. "Parents sending their children to a Montessori school may be more engaged in their education, so their own educative style at home may positively influence their success," explains Javier Bernacer at the Institute for Culture and Society, University of Navarra in Spain.