You miss the point. It can not be consensual when the teacher is indeed in a custodial role with your child. If you can't understand why, then I hope you never teach children or ever have children.
at what age can they have consensual sex with someone who is their boss?
I'm not defending a 15 year old here, because that is clearly someone who doesn't have life experiences...yet they are someone who knows right from wrong.
THe idea here, is we save them from making terrible decisions that they would otherwise regret later in life.
You are painting this very black & white and sex is a very confusing thing when it comes to "consent"
Remember, the male HAS to be stimulated and get an erection, and then push it into a vagina. It would be very difficult for a woman to force this whole process unwillingly.
The reason consent is an issue, well, because consent is an issue....we say that children are not able to give consent. Bottom line. That's probably a wise thing to do.
Now because a 15 year old might be a well matured adult or a immature turd, we sort of arbitrary pick 18 which is the age most kids are when they begin to leave high school...and chances are if you didn't go through puberty by then something is wrong with you.