I agree fully with your analysis of why it is that these schools run afoul to the Establishment Clause. I think the commentary is interesting too. I wonder though, considering the most recent SCOTUS precedent in Parents/Community Schools v. Seattle School Dist., whether we're not starting to see the balance shift with regard to issues of race and religion. In other words, where the Court has been in the past inclined to be more lenient in issues of race (Brown and its progeny are, in my opinion, rightly decided as a matter of morality, but admittedly a bit of a stretch as a matter of Con law) where it would tend to promote integration, and less malleable with respect to issues of religion where it tends to promote de facto segregation, are we now seeing the beginnings of social and governmental policy towards segregation as a whole?

I haven't thought about the issue enough to articulate it beyond the above, but it seems like if someone could piece it together, it might be interesting food for thought.