In some states it’s a hybrid of teacher student and age. For example, a state might have an overall age of consent at 16, but with a special provision of it being 19 if a teacher is involved.
In a lot of states it has nothing to do with age—it has to do with the “power” involved in the relationship.
Our corporate labor attorney used to tell us, “There are 2 million people in our region. We are telling you not to have sex with the 700 that work HERE. That shouldn’t be difficult.”
For some folks, they “covet what they see.”