Many states have websites that show what high school football games will be aired on what local station. ESPN Radio 1420 is available nationwide but typically only covers state and national high school football events.
Websites such as FloridaHSFootball.com and TSRNSports.com give alphabetical listings of team names and which local station airs live coverage of the game.
ESPN Radio 1420 is a sports radio station available everywhere. It mainly focuses on professional and college-level sporting events, but it also covers high school football games when they are state and national championships.
The National High School Broadcast Network is an online radio station that allows high schools to broadcast nationwide for free. It is only available online as of 2015.