Assessing a high school's effectiveness is not straightforward. Comparing a school's standardized test scores to those of other schools is one approach to measuring effectiveness, but a major objection to this method is that students' test scores tend to be related to students' "socioeconomic" status--family household income, for example, or parents' educational background. These factors, however, are outside a school's control. The Michigan Public High School Context and Performance Report Card is an attempt to provide a better "apples-to-apples" comparison of public high schools by adjusting their students' average standardized test scores to account for disparities in the socioeconomic status of their student populations. Socioeconomic status in the Context and Performance ("CAP") Report Card is measured by the percentage of a school's students who qualify for a free or reduced-price lunch under the federal government's National School Lunch Program. The standardized tests used in the report card are from the Michigan Merit Examination--including the ACT[R] test--taken by the schools' 11th graders from 2008 through 2011. This report card measures academic performance by using publicly available average scores on the ACT[R] and the Michigan Merit Examination, two standardized tests that all public high schools in Michigan are required to administer every year. While the report card does not capture all the variables that might impact high school performance, it does control for what is typically found to be a key variable: student "socioeconomic status." Appended are: (1) Notes on Testing Other Variables and Data Integrity; (2) Calculating CAP Scores and Letter Grades; (3) Free and Reduced-Price Lunch Weights; (4) Regression Results; (5) Filtering the List of Michigan Public High Schools; and (6) Locale Code Definitions. (Contains 19 graphs and 55 footnotes.) [This paper was written with the assistance of Marc Holley, Matthew Ladner, Jay P. Greene, Andrew J. Coulson, Lindsey Dodge, Audrey Spalding, Christina Bolema, Victoria Hechtman and Evan Burgess.]