We rigorously test for discrimination against students with foreign backgrounds in high school grading in Sweden. We analyse a random sample of national tests in the Swedish language graded both non-blindly by the student's own teacher and blindly without any identifying information. The increase in the test score due to non-blind grading is significantly higher for students with a Swedish background. This discrimination effect is sizeable, about 10% of the mean or 20% of the standard deviation of the blind test score.