Scarlet, you raise some good points. However, the study is not just private vs. public; but private religious vs public schools. Now we do not know from the report exactly what type of schools were studied.
There are a lot of things we don't know, but bear in mind, this is a news report, not the study itself. Typically, such a report will leave the reader to seek more data themselves. I do believe more information could have been included, but would like to read the actual methodology myself.
That said, I don't mind that this thread has evolved a bit into a broader discussion. I had hoped that it might do so. Still I appreciate the time you have taken to make a lucid response and input into the dialog. It is most refreshing, as well as informative.