Wis. Stat. § 119.26: Partial annexation of school district.

When the city has annexed a portion of the territory of a school district and such annexation does not include the site of any school building of such school district, the school board of the district and the board may enter into an agreement to permit pupils residing in the annexed territory to continue to attend school in the school district, and the board shall pay tuition to the school district for the pupils in accordance with s. 121.78.