I've taught sex ed for this age group! There's always at least few in the class who watch shows like "SVU" and "Criminal Minds" at home, so they can be counted on to bring up some pretty hairy topics.
During our birth control class, a child volunteered that some people use abortion as birth control, and immediately another child replied that abortion murders babies. I told them that abortion ends a pregnancy. But not everyone agrees on exactly when an embryo becomes a baby, and there are difficult questions around what exactly is best for the individual pregnant woman. HOWEVER, one thing EVERYONE agrees on is that abortion is a very serious medical procedure, and it's not something anyone would choose to do for fun. So the best thing to do is not get pregnant in the first place.
Then I asked the class, "Who here can tell me how to prevent a pregnancy from happening?"
And then we covered different methods of pregnancy prevention, including abstinence. And we discussed methods to prevent implantation of a fertilized egg, too, which brought us briefly back to abortion.
Other classes covered STDs, fetal development, power issues in relationships, roles for men and women, the impact of advertising on our self image, and lots more.
I don't think your teacher did anything wrong here. When running a sex education class it is VERY important that the children feel safe to ask any question at all (we have an anonymous question box). And it's also important that they know that their questions will be answered, and that no one will judge them for asking.
I tend to fall back a lot on, "Some people believe A, and some people believe B. What you and your family believe is up to you, but just remember - in this classroom we have respect for everyone's beliefs."