In this article, we document the trends in cognitive skills gaps across Canada. We use Programme for International Student Assessment (PISA) test scores over seven cycles, from 2000 to 2018, to provide an exhaustive portrait of the trends in the test score distribution over time and the score gaps by parental socio-economic status (SES). We find that the achievement gap between top-performing students (90th percentile) and students facing challenges (10th percentile) is large and represents more than four years of schooling. We also show that socio-economic differences in PISA scores for reading, mathematics, and science are large but generally stable over time. There are variations in SES score gaps by province, a proxy for the extent of inequality of opportunities, but these variations are not large.