MADISON, Wis. -- The American Civil Liberties Union of Wisconsin is speaking out about a Juneau County prosecutor's warning that changes to the state's sex education laws could open up teachers to criminal charges.

Gov. Jim Doyle signed a bill in February that requires schools that teach sex education to instruct students on how to use contraceptives properly. Supporters said the Healthy Youth Act will reduce teen pregnancies.

But Juneau County District Attorney Scott Southworth has sent a letter to the county's five school districts warning them that requirement promotes sexual assault. He said it's illegal for minors to have sex and teaching the use of contraceptives encourages sexual behavior.

Southworth said teachers who know students are having sex and then teach those students the use of contraceptives could be charged with contributing to the delinquency of a minor.

But Larry Dupuis, of the ACLU of Wisconsin, said Southworth has a radical view of sex education.

The ACLU believes it's common sense information to help prevent unwanted pregnancies and the spread of sexually transmitted diseases among teens.

"The law requires those teachers to also teach that about the criminal law that it would be crime for them to be having sex if they're under 18," Dupuis said.

The ACLU also said the law requires teachers to teach about the importance of abstinence.

Doyle on Wednesday also responded to Southworth's argument against the bill. Doyle said it's important for students and teens to understand the facts about sex.

"This is a common sense bill, as I said at the time I signed it. I've raised kids through that age group and God help us all who have done that -- it's not an easy time. And it's a time when we all tell our kids that the best thing to do is to abstain altogether and I think we all wish we live in a world where that is going to happen," Doyle said.

Southworth wants the schools to drop sex education until the Legislature repeals the law.