Wrong. The only difference is that it is harder to avoid the crime if both waant to participate (17 yo and 22 ye student and teacher). It is still wrong morally. It is still wrong legally. It is still wrong according to the teacher’s employment contract. It does not matter how willing the partners are. What part of that don’t you understand?
But that’s like saying there is no difference between an severe assault by an armed robber, which leaves the victim with lasting physical and psychological injuries, and a pickpocket taking someone’s wallet.
Both are crimes, and BMSkipper would not dispute that. But they are crimes of a different type and degree. They have little in common, except that both are theft.