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.
I've heard a lot of stories about Texas HS ball. We were on a playoff run and expected to win it all my senior year. We lost to the eventual state champs in the regional finals. That accounted for a lot of the high attendance at our games.
At the games I coached though, we got the players' families, some JV players getting ready for their game, and a few friends and girlfriends of the players. I coached the freshmen. Big difference.
I never coached for the glory anyway. Some of the ex-players as coaches helped me out when I started playing, and the coaching is my chance to do the same. I'll probably get back into coaching at some point once I have time.