I don't see why this is necessary. Parishes should easily be able to offer religious education classes to students who are not enrolled in parochial schools. I attended such classes during the first 4 years of my primary education, when I was attending a non-Catholic school. Later I transferred to a Catholic school, and it was no longer necessary.
Even if catering to individual religious groups doesn't pass constitutional muster, religion really needs to be better incorporated into Literature and History classes, minimum, simply for a better understanding of the object of study.
Absolutely. I went to a secular high school, but we spent a lot of time on the Bible in literature class. We also covered a good deal of Church history and philosophy in various history and social science classes.
I agree wwith you. Parents seeking religious education for their children should sign up for religion classes at their church. I don't know of any church that does not offer them in some form. As for introduction of religion classes in schools, I think many schools offer them. I was in high school in the early eighties and remember taking a world religions class then. I also remember studying churches and religions as a part of history and social studies classes. I don't remember the Bible in literature class, but then again, I don't remember anything about literature class.