Preparing students for science, technology, and engineering careers is an urgent state policy challenge. We examine the design and roll-out of a science testing requirement for high-school graduation in Massachusetts. While science test performance has improved over time for all demographic subgroups, we observe rising inequality in failure rates and retest success. English learners, almost 8% of all test-takers, account for 53% of students who never pass. We find large differences by family income, even conditional on previous test scores, that raise equity implications. Using a regression-discontinuity design, we show that barely passing the exam increases high-school graduation and college outcomes of students near the score threshold, particularly for females and students from higher-income families.