Early Montessori education shows delayed benefits for mathematical problem-solving in a 5-year longitudinal randomized controlled trial

Early childhood education may have the potential to narrow the income achievement gap. However, studies have shown substantial intervention fadeout, calling for rigorous assessment of the long-term effects of early childhood programs. In a randomized controlled study, Courtier et al. (2021) found that an adapted Montessori curriculum led to larger reading gains in kindergarten than conventional public education in France. Participants from that intervention were recovered five years later while in conventional classrooms and once again tested on academic, cognitive, and social skills (N = 97; M_age=10-11). Children who benefited from the adapted Montessori curriculum no longer showed better reading skills than their peers (d=-0.07). However, they outperformed their peers on math problem-solving (d = 0.58), an effect not present in kindergarten.