This is a fascinating thread..
I am very much pro-choice, mostly because I can't afford to adopt unwanted children. If I could solve the problem, I'd probably be pro-life.
Greaseball: Girls do not get pregnant on their own, but it's not always the boy who initiates sex. Teenaged girls frequently initiate sex because they want something small and cute to dress in fancy outfits and to love them unconditionally. You could argue that it's a self-esteem issue; I'd probably even agree with you, but you can't say that young teenaged girls never deliberately get pregnant. It's just not true.
The high school I went to had a (free) day care center (only) for students that was very nice. It was run by the YWCA and had a very long waiting list. Before the day care center, they sent pregnant girls to a separate school once they started to show; someone realized that a lot of girls went to the school only to drop out after the baby was born, and thus the day care program was begun.
I've also seen commercials on TV where a young man promises his girlfriend that he will "respect you as a human being and never pressure you to do anything you're not ready to do, especially when it comes to sex." There are "girl" ones too, but I can't remember what she says.

At the library, I noticed a sign and some pamphlets about National Adoption Month and picked up one of everything. I learned that you don't actually need a lot of money to adopt domestically; in many cases, fees for the home study, court costs, and other fees may be reimbursed, sometimes in their entirety.
The Pennsylvania Fatherhood initiative runs commercials and classes for young men & teenaged boys teaching them about contraception, what rape and statutory rape are, and what it means to be more than a sperm donor. They talk about how important it is for all men to be active in their children's lives, and why they should not only pay child support but be a physical presence and never demean their children's mothers in any way, especially not in front of their children.
I can't say that I've ever really thought of Lancaster Pennsylvania as being a very progressive place, but I suppose that in this regard it really is. The number of abortions, children in the foster care system, and unwed teenaged parents have all been dropping steadily in the area for about 10 years. I guess someone's doing something right.

What would I like to see? Parenting classes offered to younger students and to teens who are not already pregnant or parenting. We had parenting classes at my high school, but you had to be pregnant or parenting (boys took the classes too.) From what I understand, most places don't even have that. I think that if kids knew what they were getting themselves into, they'd be more inclined to listen when people talk about birth control and respecting their bodies.
Sex ed needs to happen earlier in schools. Girls are getting pregnant in 5th and 6th grade, and many of them have no idea how it happened. Myths like "you can't get pregnant the first time" and "if you stand up right away, you can't get pregnant" abound, and they are frequently believed by young girls. In my senior year sex ed class (and this was just my class of 35 kids) there were *four* pregnant or parenting girls, and two boys whose girlfriends were expecting (their) babies. And that's only the ones who sat near enough for me to talk to them or overhear their conversations. This business of closing the barn door after the horse is gone is totally not helpful.
I'd like for WIC to run cooking classes, and to continue to support breastfeeding mothers after 12 months. I'd also like to be able to buy reduced fat peanut butter and soy milk on WIC, but I could start a whole new thread on that! Teenaged girls can give birth to huge, full-term babies, but they need to know how to eat, and why. Telling them to drink milk every day doesn't do much alone; showing them pictures of babies whose mothers ate well and babies whose mothers did not will. Teaching them how to prepare a nutritious meal for themselves and their children would go a long way towards making them feel more competent as parents.
I'd like to emphasize again that I think the most important way to reduce the number of unwanted pregnancies/children is education, and at a much younger age. A story to illustrate: Last year, my niece was in Kindergarten. One afternoon on the playground, a kindergarten boy and a first grade boy held her arms while another kindergarten boy kicked her repeatedly in the shins. She did not tell her teacher, the principal, or the playground monitor. She did not tell her mother or her grandmother when she got home. She went upstairs and changed into playclothes, and that's when my mother saw her legs. "Oh", she said "some boys kicked me at school" and out came the whole story.
Now, girls don't get pregnant by being kicked in the shins, but my points are thus:
1. Boys are being taught that violence, against girls in particular, is necessary/appropriate.
2. Girls are taught that their pain is unimportant.
3. Girls agree that when boys perpetrate violent acts against them, they should just keep their mouths shut.
Does this have something to do with her mother being 15 when she was born? Not exactly, but her mother's never had great self esteem either. My niece watches her parents fight, berate, and cheat on one another constantly; they refuse to actually let go of their relationship. Even though they're not "together", it's still damaging to hear about your mother's boyfriends or your father's girlfriends. That can't be teaching her anything good about relationships.
For the record, my niece does not have particularly low self-esteem; she is bubbly and outgoing, and has many friends. (Though I'm not sure how long that will continue). It just never occurred to her that it was wrong for little boys to use her this way. I can easily see how these attitudes grow up into "Well, I didn't actually say "no", so he didn't rape me."