This paper investigates how legal cannabis access affects student performance. Identification comes from an exceptional policy introduced in the city of Maastricht which discriminated legal access based on individuals’ nationality. We apply a difference-in-difference approach using administrative panel data on over 54,000 course grades of local students enrolled at Maastricht University before and during the partial cannabis prohibition. We find that the academic performance of students who are no longer legally permitted to buy cannabis increases substantially. Grade improvements are driven by younger students, and the effects are stronger for women and low performers. In line with how THC consumption affects cognitive functioning, we find...