Well lets take this slowly.
17 years olds are still legally minors but cross the line when they act like adults and commit MURDER!
If you are 17 you can ask the court to recognize you as an adult if you wish to be independent of your parents, so many 17 years old can be recognized as adults.
Now if a 17 year old gangsta breaked into your home and raped and killed your family would you view them as a little child?
If a 15 year old boy really, really loved his male teacher like an adult, and they had sex, would you view him as an adult?