Now and then, a study comes along that sheds new light on an old debate. I came across this one via Dan Willingham, who shared it on social media, and it’s well worth a closer look. Angeline Lillard and colleagues have just published in PNAS the first national randomised controlled trial of public Montessori preschools in the United States.
How to study?
Montessori education has been around since 1907 and is now practised in over 16,000 schools worldwide. Yet, despite its reach and longevity, rigorous causal evidence of its effects has been scarce. Lillard’s team made clever use of the admission lotteries for 24 oversubscribed public Montessori schools. They examined what happens when children are (or are not) offered a place at age three. In total, 588 children were followed from preschool through to the end of kindergarten.
The results!
The results are striking. By the end of kindergarten (around age five to six), children who had been offered a Montessori place scored higher in reading, short-term memory, executive function, and theory of mind. The effect sizes range from 0.2 to 0.3 standard deviations. These are large for field-based educational research. Among those who actually remained in Montessori, there were roughly twice as many.
What’s even more interesting is the timing. Unlike most preschool programmes, where early gains tend to fade by the end of kindergarten, here the advantages emerged later. There were no significant differences at age three or four, but clear benefits by age six. The researchers suggest that this may be linked to the structure of Montessori classrooms. These mix three age groups, allowing older children to take on mentoring roles. In turn, this deepens their own learning.
There’s also a financial twist: the cost analysis found that three years of public Montessori preschool cost about $13,000 less per child than traditional programmes. This is mainly due to higher child–teacher ratios in the early years.
But wait…
Still, some caution is warranted. Only about one in five parents consented to take part in the study, and implementation quality varied across schools. Moreover, the study follows children only up to the end of kindergarten. Therefore, we don’t yet know whether the gains persist. Even so, it’s an unusually robust and ambitious piece of field research, and one that deserves attention.
As Dan Willingham neatly put it: “Finally, a large, well-designed Montessori RCT — and the results are better than most preschool programmes manage.”
