When bigger looks better: CLASS results in public Montessori preschool classrooms

The CLASS-PreK instrument is widely used to evaluate early childhood classrooms, but how classrooms using Montessori, the world's most common alternative education system, fare on CLASS is understudied. Because CLASS focuses largely on teacher-child interactions as the situs of learning, but in Montessori theory, child-environment interactions are considered more primary, Montessori classrooms may score systematically lower than conventional classrooms on CLASS. CLASS also collects format, content, and demographic information that could illuminate how Montessori classrooms compare to other classrooms. Here we used data from the first national study of public Montessori preschool to examine CLASS data in Montessori preschool classrooms as compared to a lottery-control-selected set of business-as-usual ones. Montessori classrooms (n = 54) had 50% more children on average, and significantly higher child:adult ratios (roughly 9 vs. 6) than a set of intentionally stratified control classrooms (n = 19 of 128), and CLASS scores did not differ across classroom types. Children in Montessori classrooms were observed in whole group activities during fewer cycles and in freely chosen activities during more cycles; also children were observed engaging with math content during more cycles in Montessori than in control classrooms. Counterintuitively, but consistent with Montessori theory, Montessori classrooms with larger class sizes (up to 26) had higher Emotional Support and Classroom Organization domain scores, and those with higher child:adult ratios (up to 13:1) trended towards higher Instructional Support domain scores.