For more than half a century concerns about the ability of American students to compete in a global workplace focused policymakers' attention on improving school performance generally, and student achievement in science, technology, engineering, and mathematics (STEM) specifically. In its most recent form--No Child Left Behind--there is evidence this focus led to a repurposing of instructional time to dedicate more attention to tested subjects. While this meant a narrowing of the curriculum to focus on English and mathematics at the elementary level, the effects on high school curricula have been less clear and generally absent from the research literature. In this study, we sought to explore the relationship between school improvement efforts and student achievement in science and thus explore the intersection of school reform and STEM policies. We used school-level data on state standardized test scores in English and math to identify schools as either improving or declining over three consecutive years. We then compared the science achievement of students from these schools as measured by the ACT Science exams. Our findings from three consecutive cohorts, including thousands of high school students who attended 12th grade in 2008, 2009, and 2010 indicate that students attending improving schools identified by state administered standardized tests generally performed no better on a widely administered college entrance exam with tests in science, math and English. In 2010, students from schools identified as improving in English scored nearly one-half of a point lower than their peers from declining schools on both the ACT Science and Math exams. We discuss various interpretations and implications of these results and suggest areas for future research. (Contains 2 figures, 5 tables, and 2 notes.)