There is also one "approved" method of birth control in the Catholic Church and that is the rhythm method. Doesn't always work, but it is there. The Duggars it sounds like don't even believe in that.
As for college, there are several choices that would go with their religion. Where I live, we have Bob Jones University. The women are required to wear modest dresses on campus, no make up, etc. They have a LOT of rules and it is very religious based. However, they also are apparantly a fairly decent college education wise. And have good fine arts, English and journalism programs. There are plenty of religious schools, they could choose to send their children too.
I see a lot of BJU graduates who look a lot like the Duggars and have a lot of children, etc., so it seems that there are very similarly held views.
But I think they should encourage the kids to get a higher education. BJU also promotes homeschooling as they publish a lot of homeschool curiculum for use all over the country. Knowing that, I am assuming that they get a lot of homeschooled kids at the university.