However, at the system level, across all OECD countries and all countries and economies that participated in PISA 2012 there is no clear pattern between a system's overall mathematics performance and whether students in that system spend more time in regular mathematics classes or not (Table IV.1.2).17 Since learning outcomes are the product of both the quantity and the quality of instruction time, this suggests that cross-system differences in the quality of instruction time blur the relationship between the quantity of instruction time and student performance.