I see it like this - you make sex ed early (9 or so) and progressive (introduce more and more FACTUAL concepts as the kid ages). Simply stress that if you have doubts, you may not be ready for sex and that you should be ready to accept any consequences to your actions.

Although I doubt I'll ever live to see this in the schools, it is available through the Unitarian Universalist church or the United Church of Christ:  http://en.wikipedia.org/wiki/Our_Whole_Lives
My husband trains teachers for the UU version, and the church where he works has programs for first grade, fifth grade, eighth grade, and adults. 

Believe it or not, despite it being a church, the curriculum is entirely fact-based and follows Planned Parenthood in teaching the difference between intercourse/outercourse and advocating outercourse as a safer option for teens, etc.  The program focuses on reproductive health, but also addresses the emotional and relationship aspects of sex as appropriate to each age group.  I believe the UCC version is more explicitly religious, but the UU faith doesn't even have a creed, so there's no hidden agenda.  They just really want their kids to get a comprehensive sex education. 

(I went through the antiquated program that was the precursor to this, developed in the 70s, myself, when I was in 7th grade.  It was completely secular, but it only really addressed the physical aspects of sex.)

i took workshops like this at my local uu church.  it was so awesome to get to talk with women age 60+ about sexuality, to realize that we all felt the same things no matter what age we were.  i loved going to those workshops.  and they always had coffee.  someone said uu's always have coffee.  haha.  it was certainly true.  BUT they would only brew and sell fair trade coffee.  : )

I think its a little funny that in my school district, whe started having sex education in (I think) 6th grade and had more and more comprehensive education as the years went on and a lot of girls in high school got pregnant...... I valued all the sex education because I knew in other places kids were told misleading/ untrue things and I really felt (and still feel) bad for them.

I'm 21 and still a virgin and intend to keep it that way until I find someone deserving of me whom I love and who loves me. I used to hate not being with someone and being a virgin, but now I sort of like it and I think its really special.

Oh and I never made any pledge, but I guess what I just said sort of counts...

I can't add anything that hasn't already been said, but I will add my personal experience for everyone's entertainment.  I signed one of those virginity pledges in high school at my church.  I participtated in this whole program called "True Love Waits."  As a 16 year old, I even wrote a letter to my future husband with the intentions of giving it to him on our wedding night...explaining how I saved myself for him and all that good stuff.  hmm.. I should go look for that!  Anyway, I was always very proud of my virginity and was hell bent on keeping it until my wedding night.............until I decided not to wait anymore.  ha.  It was shortly after my 20th bday (on Easter sunday, no less). 

Now, I did not not abstain from sex until I was 20 because of some stupid (imo) pledge or stupid (again imo)"true love waits" program.  I knew plenty of people who participated in the program who were actively having sex!  I signed the pledge and did the program BECAUSE I wanted to remain a virgin.  Anyway, I was super religious and bought into remaining pure till marriage so that i could go to heaven and stuff.  I'm not exactly sure what made me change my mind.  i mean...i loved the first guy i slept with and all but i knew we weren't gonna get married or anything.  I just decided I wanted to do it. 

I've been thinking about this a lot lately.  Somewhere along the way, I came to the realization that I've never felt bad about having sex with anyone I've been with and the only reason I would've felt bad was b/c society (i.e. my church) told me it was bad.  I just don't buy it anymore.  Like kmk said, people are sexual.  Teach them how to make good decisions. 

I believe in being realistic.  When Angel got her period we had a talk.  When she started high school we had a much more in depth talk and I warned her that there would be pregnant girls in school.  She scoffed and rolled her eyes.  About a week in, she called me and told me I was right.

At 15 I took her to a Planned Parenthood clinic and got her on BCP and condoms.  Not because she was or would be sexually active but because I did not want her to be unprepared, unaware or unprotected.  I would rather know that she is safe, not if she is innocent or not.  Especially pregnancy is one of the least worrying things about unprotected sex.