To examine the amount of control parents have over the education of their children, and the extent to which states encourage market-like competition between schools, we used an index of three different metrics. First, we calculated the market share for schools of choice in the state—that is, the percentage of students in charter schools, attending private school at their own expense, or attending private schools with support from a school voucher, tuition tax credit, or education savings account for the 2011–2012 school year (those in private school as a result of a private school choice program were counted twice).
We also used the National Alliance for Public Charter Schools’ grading scale on the strength of various state charter school laws, expressed as a percentage of the total points available in the grading rubric. Finally, we used the Center for Education Reform’s (CER's) Parent Power Index to examine the impact of charter school law strength as well as other reforms intended to increase the say parents have in the education of their children.
Each of these three metrics was calculated as a simple percentage, averaged together, ranked, and then curved to have 10 A’s, 10 B’s, 11 C’s, 10 D’s, and 10 F’s.