Wisconsin laws are a bit of a confused mess when it comes to their weapons laws.
Under the State Fair Park Board's section 2.14, however, the "dangerous weapons" definition includes knives:
https://docs.legis.wisconsin.gov/code/admin_code/sfp/2/14
If you plan on carrying a knife, concealed or otherwise, check with the local police first. There
are laws that apply to possession of a dangerous weapon by a person under the age of 18, but the "where" and "why" of carry can make a difference.
With any weapon, avoid school zones.