Who should the responsibility of sex education fall to?

Personally, I think we need better sex education than what we have now considering some of the questions I've seen, but it got me thinking, who should have the responsibility of teaching kids and teenagers about sex?

For instance, I was one of the oldest of my cousins so around the time I was curious about sex, my aunts were all having their kids and being an avid reader, I tore into every pregnancy and medical book I could get my hands on. Plus, I was fortunate enough to have a mother who was willing to answer my questions and encouraged me to read these pregnancy and medical books. Sex was never a taboo subject with her and I always felt I could ask any question I had without shame. And I think she'd rather I get my information from her or a medical book than somewhere else.

But I know not everyone is that fortunate. And I've heard of parents being concerned about their kids learning about sex in school. (I was homeschooled through high school so this never came up for me) But wouldn't it be better for them to learn from a reliable source like a teacher instead of their peers? Or should they figure it out on their own through proper research?

Just curious to hear everyone's thoughts.