Policymakers have attempted to increase academic preparation and equitable opportunities to learn science by increasing science course graduation requirements in nearly every state. In Michigan, the Michigan Merit Curriculum required the graduating high school class of 2011 to, among other requirements, obtain three science credits including biology and either chemistry or physics. Many studies have shown a relationship between science coursework in high school and postsecondary STEM outcomes like choosing a STEM major or graduating with a STEM degree. However, these studies suffer from self-selection issues meaning that we cannot interpret the estimates as causal. Meanwhile, quasi-experimental studies of course requirement policies have found disappointing effects of science coursework requirements on achievement and graduation outcomes. Using detailed high school transcript data from the years before and after the implementation of the Michigan Merit Curriculum, I estimate the effect of the Michigan Merit Curriculum on science course-taking and characterize the changes in science course pathways. I also investigate how the policy differentially affected schools based on a variety of school characteristics. My second aim is to provide evidence about the effect of taking science coursework on postsecondary STEM outcomes related to field of study and college course-taking. I find that before the Michigan Merit Curriculum was implemented, a relatively small proportion of students, less than 30% of students met all of the science course requirements that the Michigan Merit Curriculum called for. After the policy was put in place, there was no change in the number of total science credits students took, but students took about .08 fewer biology credits, .14 more chemistry credits, and .07 more physics credits in high school. The number of students meeting all Michigan Merit Curriculum science requirements increased by 6 percentage points. Difference-in-differences analyses indicate that the policy affected the schools where the fewest students met the Michigan Merit Curriculum science requirements before the policy.I also show that after the Michigan Merit Curriculum students were 1 percentage point more likely to major in STEM, including .5 percentage points more likely to major in biology and .7 percentage points more likely to major in engineering. Students were also slightly more likely to graduate with degrees in the physical sciences. However, these differences in postsecondary outcomes were largely driven by the most advantaged students. In many cases, students who have traditionally been well-served in STEM subjects increased the rate of majoring and graduating with STEM degrees, but for groups that have not-females, racial/ethnic minority students, and students with the lowest achievement-the rates stayed largely the same. Overall, results suggest that although there were changes in course-taking patterns for students that were not meeting the requirements prior to the Michigan Merit Curriculum, the long-term gains were most experienced by students who were already well-served in science.Instrumental variable analyses seeking to understand the causal relationship between chemistry and physics course-taking in high school and postsecondary outcomes showed inconsistent results, although there was evidence that being induced to take chemistry or physics in high school was beneficial for encouraging students to take physical science courses early in college and improved grades in some college STEM disciplines.
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