There is . . . and since the 1970s has been . . . a national outdoor high school t&f championship . . . the USATF Junior Nationals.
Some 50-60 years ago the defacto hs championship meet was Golden West.
Then Keebler/International Prep Invitational joined in, diluting the Golden West fields on occasion.
National Scholastic Sports Foundation then began recruiting nationwide in the 1990s for its NSSF/NON/NBON meets, eventually helping to kill off the IPI meet and reducing GW to a local affair for kids in NorCal who want to run another meet after CIF.
Fortunately, what high-level meets we have today. . . New Balance Outdoor Nationals, adidas Boston, Brooks PR, Midwest Distance Classic . .. have directors who are smart enough not to compete head-2-head with USATF Jr Nats . . . especially important every two years such a now when the top two qualifiers advance to World Jrs (now called World U20 Champs).
As such, they must hold their meets the week or two preceding Jr Nats so they invariably compete amoungst themselves for talent.
What makes NBON unique is its equal emphasis on relays. None of the other meets have relay races. So, practically, the relay team winners can call themselves national champions. Furthermore, it appears that all high school national relay records are being set at this meet.
Therefore, if you want to crown unofficial individual high school national champions, check out the results of Jr Nats this weekend from Clovis, CA (where the CA state meet is held). There are college frosh mixed in, but for events attracting top hs talent, the top hs finisher is, for practical purposes, the national champion.
Pay special attention to the w1500m where Kate Murphy, Christina Aragon and Katie Rainsberger race against (collegian pro) Alexa Efraimson . . . an example of just one event where the top preps are facing off against each other.