I got curious and looked it up. This is where Barnes probably falls in because I believe he has been there for over 5 years.
E. A person who has served as a non-faculty assistant coach in football, basketball, baseball, girls' softball, and track may become a head coach in that sport if that person has five or more years of experience as an assistant coach and has taken the ASEP Coaches Education Course in a TSSAA-approved course and completed the TSSAA Online Coaches Training Session. This is from page 10 of the Handbook.
I also found out if you are using a volunteer coach and they havent gone through the TSSAA the chool will be fined $500. Interesting because I know a lot of schools that would get nailed by this rule.