Subjects like "same sex relationships", in my opinion have no place in a student's curriculum, and that may make me a prude.
Sex education should be basic, and mainly geared toward anatomy, with an explanation about the function of body parts. Students should be taught about STD's and how they are transmitted, and pregnancy. Also, that the only 100% full proof way to not end up experiencing either, is abstinence.
It's not the school's responsibility to teach what they feel is right or wrong on a moral level. Any additional information should be between the students and their parents.