Student access to education levels, tracks or bachelor specialties is usually determined by their previous performance, measured either by internal exams, designed and graded by teachers in school, or external exams, designed and graded by central authorities. We say teachers in school grade on a curve whenever having better performing peers harms the grade obtained and hence the evaluation of a given student. We use rich administrative records from public schools in Catalonia to provide evidence that teachers indeed grade on a curve, leading to negative peer effects. We find suggestive evidence that these negative effects impact school choice only the year when internal grades have an impact on future prospects.