>In other words, sure, if you skim off the brightest and most motivated kids and put them in a different school, hey presto! they'll perform better than the ones left behind. This proves NOTHING about either public or private schools. Hell, it hardly even SHOWS anything, let alone prove.

Most kids can suffer the same fate if schools concentrated on teaching and motivation. Who says there is any organized skimming anyway? The fact is that private schools (religious or not) do a much better job of educating than do public schools, for many reasons. The conspiracy is on the part of parents who want better for their child. Why not make this choice available to those who cannot afford it? Why reward failure in the government schools? Competition for the government schools is good medicine!