Each year over two million secondary-school students across English-speaking West Africa sit coordinated exams, with the explicit goal of maintaining consistent educational standards across schools and over time. Nevertheless, pass rates fluctuate from year to year, fueling speculation about cheating and short-term effects of education policies. To test these hypotheses, we construct an item bank of past exam questions spanning 2011-2019, and administer a hybrid test to 4,380 Ghanaian students. Scores across math items drawn from different exam years - when taken by an identical group of students on the same day - closely track fluctuations in Ghana’s national pass rates over time, absent any role for cheating or changes in real performance. Large swings in exam difficulty have significant implications for fairness and efficiency: half of candidates who failed to pass the maths test in 2015 would have passed in 2019.