Actually, if it is a “practice” as you say, it would be like a scrimmage which isn’t extracurricular and the student could participate. Our district had a district only practice UIL Concert Contest and all students could participate regardless of current eligibility. Okayed by the State UIL Office using the scrimmage explanation.

However, as has been said on here many times, it’s better to call UIL than trust the advice on the Yellow Board on an issue like this.