From the discussion above and think more deeply, I think the question is not whether sex education should be taught in school or not, but how it should be taught, protecting teenagers from getting hurt.

Sex education should be taught in schools, for too many students do not know clearly about it. When children get physically mature, they may want to have sex, while they may not know how to protect themselves as well. Especially for girls, they may get more hurt than boys.
在学校里应该开展性教育，因为太多的学生并不清楚地了解它。当孩子们身体发育成熟，他们可能会想做爱，但是他们也许可能不知道如何保护好自己。特别是女孩子，她们受到的伤害可能会比男孩更多。
Teens need to be given guidelines to help them protect themselves. The US has more than a million teenagers being pregnant each year. Teenagers have the highest rate of sexual transmitted diseases. Of any age group, one in four young people contract an STD by the age of 21, and the number of HIV infection increases rapidly among young people. In addition, if teenagers have an unprotected sex, they may have a chance to have a baby, and base on their young age, less experience, and no income, the young father and mother have no choice but to abort the child. Those innocent babies who deserve to born to the world and live under the sun are killed by their ignorant parents.
青少年需要获得指导来帮助他们保护自己。美国每年有超过一百万的青少年怀孕。青少年感染性传播疾病的可能性最大。在任何年龄段中，四个21岁的年轻人中就有一个染上性病而且艾滋病病毒在年轻人当中感染速度在迅速增加。此外，如果青少年有不安全的性行为，他们可能有机会怀上孩子，而且由于他们年龄太小了，经验少，没有收入，年轻的父母没有别的选择只能选择不要那个孩子。那些应该来到这个世上、在阳光下生活的无辜的婴儿却死于他们父母的无知中。
So, sex education must be taught in school. Besides, Chinese parents are always shamed of telling their children about sex. From the discussion above and think more deeply, I think the question is not whether sex education should be taught in school or not, but how it should be taught, protecting teenagers from getting hurt.  
所以，学校必须开展性教育。此外，中国的父母总是羞于告诉孩子们关于性的问题。从上面的讨论并进行更深入的思考，我认为问题不在于是否该在学校开展性教育，而是该如何教，从而保护青少年免受伤害。