I'm going to express a bit of dissent (but only a bit, hehe).
While I think it would be horrible for a teen (or child) to choose to abort a pregnancy when her parents were willing and able to care for the resulting child, the parents are not the ones enduring the pregnancy.
It's not their body, not their choice.
Viewing abortion as a medical procedure, I am tentatively in favor of required parental permission in most cases, but I think it would be wrong for parents to make the decision for the pregnant teen. And I do think there is a distinction between right and wrong and legal and illegal. Many legal things are wrong, and there are legal things that many would argue are right or at least not a danger to society.
So, with parental consent being required (which I am slightly in favor of), it should be legal or allowed, but it's not something I think is appropriate or correct.