Normally, I would agree with you about this sort of thing, but the girls who are at the highest risk of this probably have parents who never would opt in. "Parents" is probably being generous, since dad might not well live there.
You're certainly smart enough to opt out if you think that's a great decision, but the default ought to be to get the vaccine.
This is the same reasoning that gets us sex ed for kindergardners. "Oh, we have to teach them all the facts early, some parents just won't take the responsibility." It's getting us schools that track our kids weight and body mass to be sure they aren't eating the wrong foods. "Oh, Janie, be sure to tell mom to give you more carrots and fewer cookies!"
It Takes a Village to take away the rights of responsible parents, because others "might not" be responsible.