In Wisconsin it's illegal for anyone under 18 to have sex with anyone - even other minors. Generally "contributing to the delinquency of a minor" is defined as any act that knowingly encourages or enables a minor to commit a crime.
So, since having sex while under 18 is a crime, this fellow (a Republican Baptist, to no one's surprise) claims that if teachers follow another state law requiring them to teach the use of condoms and contraceptives, he will charge them with CDM. Basically, he's claiming that it's equivalent to teaching them to use burglary tools and case houses.
His innocent claim - that, gosh, he'd really rather not have to do that, but his hands are tied - is a silly as the idea of prosecuting these people.
But to show you just how stupid the law can get in Wisconsin, check this: children under 17 who have sex with other children are charged as juveniles. But once they hit 17 (but are not yet 18) they're charged as adults.
Get it? They're sufficiently "adult" to face charges for something that is illegal only because they aren't adults.