Wis. Stat. § 938.12: Jurisdiction over juveniles alleged to be delinquent.

(1) In general. The court has exclusive jurisdiction, except as provided in ss. 938.17, 938.18, and 938.183, over any juvenile 10 years of age or older who is alleged to be delinquent.

(2) Seventeen-year-olds. If a petition alleging that a juvenile is delinquent is filed before the juvenile is 17 years of age, but the juvenile becomes 17 years of age before admitting the facts of the petition at the plea hearing or if the juvenile denies the facts, before an adjudication, the court retains jurisdiction over the case.