SuperNationals: Once every four years (the following three spring tournaments combined, can be as many as 5,000 people)
Spring Nationals: There are three tournaments in elementary school, middle school and high school.
The K-12 Grade National Championship (this weekend's tournament) has already had a record-breaking attendance of over 2,300 this year.
Online National Scholastic Quick Championships: I don’t know if the tournament after the epidemic will continue in the future
National Youth Action Championships: not popular
Junior Chess Congress: not popular
U.S. Junior Open: The only bright spot, the winner can participate in the US Junior Closed, the top invitational tournament for students.
All-Girls Nationals: It's KCF in the spring, in Chicago. The number of participants is 300-400.
These are all tournaments that are fully open to elementary and middle school students studying in the United States.