I myself would be more comfortable talking about things like this with a class, but, especially if they don't split the class by gender, things might get awkward for some people. This can also be the case with physical bullying.
I do understand that teens have to learn this stuff eventually for their own protection, but some may want to do it in a more private fashion, understandably, and should be able to step out of class.
As with most schools, there is always a fraction of the parents of students who will be unhappy with various education topics. Providing sex education is a sensitive subject and parents need to have the option to allow their students to skip the material if they choose. Complaints can be a helpful way to monitor how the sex education material is presented.
Many children have questions about reproduction and sex, but they may not feel comfortable discussing these issues with their parents. Sex education gives them an opportunity to learn about sex and reproduction without having to ask questions and to feel comfortable discussing these issues in a non-judgmental setting with others.
Teachers should focus on providing accurate information in a sensitive manner when it comes to sex education. They should not have to focus on how to handle complaints. Sex education is important, teenagers have to learn the fundamentals and the risks associated with sex so that they do not find themselves in a precarious position.
Teachers have more to worry about than addressing ethics complaints about sex ed. Sex
Sex ed curriculums should b decided on by a panel of experts and these people should be train to handle the ethical concerns of the community. The job of the teacher should simply be to teach.