That's shocking, especially for an area with such HS football tradition.
I was a volunteer coach part/time(during 2 a days, off season liftings, games) for the freshmen at a fairly bigtime HS program(we got 8000+ at a varsity game, and one, maybe two NFL'ers one our team) for 4 years while I was in college. I wasn't an employee. We had other part timers, usually ex-players as I was. At the freshman level, only our head coach (and one assistant during two of the years) was a teacher.
However, the point I was making was that Texas spends way too much money on sports programs - having full time coaches for the major sports (football/basketball/baseball) who "might" handle a class or two of History during the day, but otherwise do coach stuff all day -
Your program, as well as the one where my daughter graduated, used a full time teacher who wanted a bit of extra money on the side - did the coaching after school - it isn't like that in Texas - it is a full time, high paid position, where a couple of winning seasons means you are recruited to move to a bigger school district with a bigger salary and you take your "assistant" coaches with you - Football coaches in Texas, who are winners, are treated like Kings -
I went to a class A (biggest) high school in Michigan and a class 5A (biggest) high school in Texas. I can vouch that 8,000+ at a Michigan high school game is big time. (I don't think my high school pulled 8,000+ when we played our rival at the last game of the season. And that was counting the rival team's fans, too!) I will also state that 8,000+ at a Texas high school game is below average.