First: you have activated an old post. It is doubtful the OP will be back now.
"Doesn't old reccords clear by age 18 ?"
Not when it comes to sexual offenses.
"And about the 18 years old teenager with the 13 years old girl, it's no rape, even if the guy is over 18."
Yes it is. Many states have enacted laws that it doesn't matter if one party is of age to consent. If there is an age difference between the two greater than a specified number of years it is statutory rape. In some states it is as little as 3-4 years in most it is 5 years in age difference.
"She was under 15, legal age of consent. But did she lie on age ?"
The age of consent in some states is 15 but if there is a significant age difference it can still be charged as rape. It doesn't matter if the minor lies about their age. The burden is on the person who is older to accurately verify age and NOT get involved if there is the slightest uncertainty.
"Where did the boy meet the girl ?"
Irrelevant.
"If it's in her middle school, it's his fault."
Not according to the law.
"If she was in a place forbidden to kids and she lied about age, the guy is the victim and the parents of the girl should be taken as responsibles."
Not under the law. It doesn't work that way.
"Where were they when their child went out to play with her physics and pretended to be an adult?"
What you fail to understand is it doesn't matter. The older of the two involved with each other bears the burden of NOT getting involved with a minor. That is how the law works.
"It's easy for a girl 13 to pretend she's 16."
Doesn't matter if the minor pretends to be 18. The burden is on the other person to KNOW their age and NOT get involved when they find out the other person is a minor.