I think the best approach with our children is to talk to them at their level. Ten years old is pretty young to get into all the details regarding chastity. It is not too young to ask if they know if any of their friends have a girlfriend. (My kids could name people in 4th grade who were dating.) Their version of dating being quite different than our own. But by asking, and talking and keeping those lines of communication open, you become priveleged to learn where they are at and what they are thinking. It's gives us an opportunity to discuss our views. And by talking often and reinforcing values, they will remember and learn.
For instance, for my son's whole life, I have said that if he wants someone to do something and they say "no", he needs to respect that. It applies differently now than it did when he was much younger. Also, I have enacted scenario's for saying no to drugs. I have given them the reply to use when asked. "I'm too smart to do anything that dumb." When they go someplace on their own, unsupervised, we go over the rules, "You are not alone out there, you represent your family. Never do anything that would not make me proud of you." Even his friends (I give a lot of rides) will chime in and repeat it as soon as I say the words, "Now remember."
Learning about sexuality is no different than any life lesson. It is about open communication, asking the tough questions and teaching them our values. I was shocked to learn that my neighbors had never discussed their values with their daughter whom they had found out had a boyfriend when she was 16. They were freaking out after catching him leaving their home. I asked if they ever taught her boundaries, they hadn't and asked me to discuss it with her. (She is at my house a lot, so she has heard many of my conversations regarding this.) I teach my children to respect themselves and others. Words their friends use are not allowed. Movies their friends see are not permitted. I'm not naive enough to know I can protect them from everything. But I am concerned enough to give them the tools to help them for when I can't be there.