True. And today I was reading that some Hogwarts Running Club people were leaving roses at Snape's door (in the FJ queue?) and having a moment of silence...it might be mystifying to those halfway through (who didn't have faith like my family did!) why some might do that. Also mystifying why someone would be proud to have a Snape wand! They might get some hints.
Then again, we're kidding ourselves if we think our kids don't know. My son is homeschooled and goes to the Y for dance classes. And while we were reading the last books he mentioned it, and some random elementary school kids at the "drop in zone" at the Y told him just about everything.
It's been 20 years since the first book. People know and people talk.