Spain just recently raised the age at which females could legally have sex from 12 to 16. There is an island somewhere in the Pacific where one man has the job of de-virginizing every girl when they reach the age of 12. It is his actual job. (Or at least it was in the 90's when I heard the story on NPR.) And after that the girls and all boys of the same age are free to have all the sex they want. Go figure.
I had a great great great grandmother who got married at age 12 to a 14 year old. She died at the age of 28 giving birth to her 14th kid.
The norm varies. In our American culture, right now, it is indeed considered wrong. This is for two reasons. One, we now realize that it is harmful, physically, for a female to have sex at too young an age. If nothing else, it increases her chance of getting certain cancers if she is sexually active before the age of 13. And second, we have extended childhood into the late teens and have decided that said childhood should not include sex. On top of that, there is no way for a child that young to meet the needs of a newborn, or oversee the raising of a child while she herself is still one.
There are obviously individuals and groups within America who feel differently. Be they mormons or pedophiles. That is, there are people who are willing to harm or chance harming children for their own selfish gratification. The imbalance between the emotional and physical needs of a child and the wanton lack of concern for others exhibited by some needs to come down on the side of the child.
So yep, it is morally wrong. In my strong opinion.