Using a difference-in-differences framework, we estimate the impact of Ramadan on educational outcomes of Muslim students living in a non-Muslim country. For identification we exploit that the number of Ramadan weeks during the course that we study, varies from year to year, ranging from zero to four. Our main finding is that Ramadan observance has a negative impact on performance; one additional Ramadan week lowers the final grade of Muslim students by almost 10% of a standard deviation. (Contains 1 figure and 8 tables.)