That said, why did the locals keep pigs, if not to eat them?
I have a feeling that the Gaderenes weren't Jews. So they could eat what they liked...
With regard to teaching religion in schools, particularly Christianity. Christianity has been a key driver of historical events for hundreds of years; think of Henry VIII, the Spanish Armada (and the RC plots to depose Eliz I), the English Civil War, the deposition of King James II. And, much nearer in time, the Troubles in Northern Ireland. They are all very closely connected to religion. How can children understand our history without knowing about Christianity and the deep divisions it led to.
It's a difficult one, I know, because I think that, having had it explained to them, our very secular children would probably be astounded and disbelieving that religion could have such a key role.