Why shouldn't abortion be used as a method of birth control? Or, more specifically, why should the law step in and mandate that it not be used as a method of birth control? If someone prefers a series of minor outpatient surgeries to condoms or hormonal medications, why should the law be telling them they can't? What public interest is served?
I don't think the ultimate goal is for every pregnancy to be intentional. That's impossible, and irrelevant. The goal is, and should be, for every child carried to term to be wanted. And the corollary to that is that if a child is unwanted, it shouldn't be carried to term, and nothing should be forcing pregnant women to carry an unwanted pregnancy to term. Restrictions on the mother, like "Can't get an abortion without sitting through a sex ed class", are just obstacles getting in the way of terminating unwanted pregnancies, just like laws mandating parental or spousal notification.
Education is good. Education should be somewhere. Requiring a class before you get an abortion isn't where it should be. And educated people can, and do, still make irresponsible decisions, or do not want children, and there is no 100% method of effective birth control in sex. If you think abortion ought to be viewed as a last resort, that's fine, but you can't mandate that.