I went to an all girls school so i didnt have much choice
In primary school us girls got taken out to have the 'period talk', whilst the boys carried on doing maths

Sometimes its good to be a girl! We then had co-ed for a bit of biology, but it was all on video!
In year 7 we had a male teacher teach us the biology again, in case someone had missed that lesson! He was so uncomfortable, it was very funny (for us, not him, i felt bad for him).
In year 9 (13-14) we had the 'peer relations' bit, where they talked about contraception (although it was a bit late in the day for that for many girls in our class

) we had a female teacher who was a blast and kept on making jokes. We also got taught about alcohol, drugs etc. which was really good to talk about. The only problem is we didnt have enough models to go round when doing one form of contraception, so i missed out on that bit.
I dont think i would of liked to do it co-ed cause they guys wouldnt take it seriously, or tease the girls. it was quite nice doing it single sex, but then maybe meeting up and discussing what we learnt.
I am also 100% against only teaching kids abstince, it actually increases risk of teenage preganacies and diseases.