My kids are young, so can't answer that part yet.
My younger sister told my other sister. Not right away, but kind of soon after. We went into "inform her about everything" mode--from contraception and STD prevention, to what makes for a good relationship. And we got her a copy of Our Bodies, Ourselves.
But parents, no, did not tell parents. Parents were, however, not oblivious to the possibilities. Mother especially had always been informative about biology, even at a young age, and both were always informative about being respectful and respected in any close friendship or romantic relationship. I think the message generally was: "It's never wrong to wait."
What I think was missing was access to birth control through the parents. Oral contraceptives: not made available, because no communication on this front. Not sure that parents would've ponied up for this, either. I think they've have adopted a strategy of "You're too young, we won't pay because it feels like we support it." Hmmm, this is an interesting thought experiment: What would they have done??? Maybe they'd have told us to earn our own money to pay? I don't know...