You can host a showcase in January (ex. anytime during the season) with your team at your school. However, when you start inviting other teams by definition of IHSA By-laws it becomes at contest, even if judges are not present. A showcase, with multiple schools invited to perform, is classified in the Athletic By-laws as a scrimmage.
58) SCRIMMAGE AS CONTEST
Q. Is a scrimmage considered to be a practice or an interscholastic contest?
A. If a scrimmage involves exclusively students from one high school, it is considered to be practice. If a scrimmage involves students from more than one high school, it is viewed to be an interscholastic contest and is subject to all rules pertaining thereto. (Constitution 1.420 & By-law 2.090)