TSSAA is confusing, I would initially agree that JV is not sanctioned and here is an excerpt from their website:
At the junior varsity or B-Team level, the only eligibility rules that apply are those in Sections 1 (Enrollment), 2 through 4 (Academic Rules), 5 (High School Graduate), 6 (Eight-Semester Rule), 7 (Repeating Rule), 8 (Eighth Grade Participation), 9 (Age Limit), and 10 (Physical Examination and Parental Consent). At the varsity level, all eligibility rules apply.