There's a number of things that make a priest abusing a kid seem less sinister than a teacher doing it... like for example that since priests are male, there's probably penetration when the kids are molested, while most of the molesting teachers are female, so the abuse is less invasive. There's also the fact that priests are percieved as sexless by the kids, while with female teachers it's exactly the opposite... especially if they're hot as a great number of them seem to be (You don't wank to your priest when you're in sixth grade...). So, the "leap" when the priests end up being pervs is greater in perception than when it happens with a teacher.