Soemthing rubs me the wrong way with this approach. It's not an issue of public or private schools,...and I favor private schools from higher criterion of excellence,....but the isues being discussed are closer to literacy, illeteracy, and any student simply giving a damn.
I don't attribute the diference in ability to 'test-taking skills'. I find the test scores are remarkably higher if one simply knows and has learnt the subject.