Healthy Schools Campaign https://healthyschoolscampaign.org/programs/cooking-up-change/national/
Careers Through Culinary Arts Programs https://ccapinc.org/program/cooking-competitions/
Culinary Institute of New York http://ciny.monroecollege.edu/americas-best-hs-chef.html - (this one has passed, but you could practice so you're ready for 2021 if it opens up in the new year)
Want to hold a cooking competition? Here are the steps: https://www.educateiowa.gov/sites/files/ed/documents/1314_np_sm_Cookingcontest.pdf
Healthy Kids Cook Off: https://everykidcancook.org/cookoff/
In the middle of this page, there are numerous contests and websites with links: https://thecheapgourmet.typepad.com/the_cheap_gourmet/cooking-contests.html
Junior Chef Competitions https://www.thelunchbox.org/lunchroom-education/junior-chef-competitions