Would you consider watching your local upper school teams play each other in a sporting competition? No, I didn't think so. It's a very big thing here. In fact, as I type this the boy's basketball state championship in being played, and it's being shown on TV. My wife assures me that it's a big thing. She remembers when her high school went to the state championships. I was in my upper school's hockey team, but it wasn't on TV and no-one came to watch, not even any parents. Over here, it's not just the parents that attend the games, but school kids themselves will turn out to watch their classmates play.
The state I live in is only slightly smaller than England but has 45 million fewer inhabitants. The state is mainly rural, but on a grand scale and it's easy to see how high school teams can attract so much attention. For me, watching a team of 17-year olds play sport on TV is bizarre, but I didn't grow up in a culture that's so obsessed by sport. Actually, in England we enjoy watching sport, but we don't have the same ideology associated with sport in our culture. In the USA, sport is encouraged much more throughout school. Playing sport seems to be much more virtuous, and there is a sense that encouraging your child in sports is something a good middle-class parent should be doing. There is also more money invested in sport. Playing sport at the university level is a big thing and ESPN (the major sports network) even tracks the best high school prospects throughout the country.
Sport is just a very big thing over here, and people are interested in it at all levels.