https://www.statista.com/statistics/267955/participation-in-us-high-school-football/
1,039,079 total high school football players (11-player gridiron) in the 2017/18 school year (1,036,842 male, 2,237 female)

High school football participation continues to drop as concerns over cost, injuries persist
https://www.washingtonpost.com/news/early-lead/wp/2018/08/28/high-school-football-participation-continues-to-drop-as-concerns-over-cost-injuries-persist/

The problems facing high school football don’t appear to be going away, and according to new data released by the National Federation of State High School Associations, neither is the downward trend in participation.

Fewer than 1.04 million high school students played football in 2017. That’s 20,000 fewer athletes than in 2016, a 2 percent drop. [emphasis added.]

What does this have to do with gun owners? Compare the numbers.

A two percent drop in high school football player participation is about the total amount of current card-carrying USPSA or IDPA members.

And that’s just gridiron football. High school basketball has about the same total number with nearly one million participants.
https://www.statista.com/statistics/267942/participation-in-us-high-school-basketball/

Add in nearly a million high school soccer players, about a half million high school baseball players, another half million for volleyball, and a 1/3 million for softball and you have more active ball sport participants in high school than the NRA has total members.

Click to access 2014-15_Participation_Survey_Results.pdf

https://www.nfhs.org/ParticipationStatics/ParticipationStatics.aspx/

And these numbers are active participants and does not count spectators, fans, supportive friends and family, and any other non-player that is involved.

As far as shooting, there are just over 5,000 high school marksmanship competitors (1,025 Air Rifle and 4,238 Riflery). And before you wrongly assume this is due to some anti-gun policy at the schools, consider that only about 2% of NRA members hold a Classification, something that can be earned by merely participating in a Sanctioned (Registered or Approved) tournament.
https://firearmusernetwork.com/nra-classification-fall-off/

These are the real reasons ball sports get media coverage and shooting does not.