Secondary school class sizes and student performance in Canada, which compares provincial class sizes and test scores from the OECD’s Programme for International Student Assessment (PISA), finds that Saskatchewan had the smallest average secondary school class size (22.6 students) among all 10 provinces but the lowest test scores in all three PISA subjects—reading, math and science. And Ontario had the smallest class size (24.8 students) and lowest test scores among the four largest provinces.