Weston's Graduation Pie Bake-off

Susan Weston thinks that,

Public and nonpublic graduates and nongraduates, when combined, should add up to a credible estimate of that year's eighteen-year-olds...

[M]ost approaches to public school graduation rates make the same big mistake. Specifically, they assume that many students who spend two years in ninth-grade can across the stage with their first freshman class and with their second freshman class, collecting diplomas both times. Those approaches either result in implausibly low nonpublic school numbers or implausibly high numbers old enough to graduate.

So she's gone into the kitchen to bake up some illustrative graduation rate pie graphs for your consumption. Yum.