Planned Parenthood says it can work if the couple are both on board with it working, if the man has VERY good control (he has to pull out before
the orgasm starts, if he urinates before you begin to have sex, so that the urethra is cleared out, and if it is practiced to the letter.
My husband and I have used this for years. I get pregnant at the drop of a hat. I've never gotten pregnant from withdrawal, except once when I thought I was in my "Safe Time" and I asked him not to pull out. But, that's a problem with Natural Family Planning (which is a bust in our house) other than withdrawal.
I have some doubts whether most teenage boys have enough control to do this accurately, but those who have the control and know the way to do it should have a near 97% protection rate.
It's not "ignorant" at all.
I'm a nurse and my husband is a Senior Staff Engineer, we're educated people and educated about sex. We wouldn't be using an "ignorant" birth control method.
However, this method does take dedication and control. One slip up and your protection is not going to be there. Personally, I'd rather see teens using condoms, as it also adds a layer of protection against pregnancy and protection from disease. It's also harder to mess up condoms.
Here's the Planned Parenthood Information
on how to properly use withdrawal, who it works well for and how and when to use it, as well as the effectiveness rate.