@skyofstars I am not sure that you fully understand what “repeating” a year entails. It does not mean taking all of the same classes over again, or being in anyway ahead of your peers, or that you will not be extremely challenged in your classes. Any school who allows repeats will work with you to create a class schedule that ensures you’re not actually “repeating” course material that you’ve already learned. You just get one more year to take interesting electives, peruse EC interests, and maybe do another program like studying abroad.
I agree with @stalecookies, it seems as though you view being the youngest as a badge of honor. I get that, I really do. In 8th grade I was able to skip two school years of coursework and take all 10th grade classes, making me over a year younger than everyone else I was around. This past school year I was also the only 9th grade student in every one of my courses except gym. It feels good to be doing the same work as older students when you’re multiple years younger. But to be completely honest, it is a very dumb thing to be proud of. It gives you absolutely zero advantage in college admissions, and when you get older you end up not being able to participate with your peers in activities involving driving or drinking (not at the same time ofc!). Although you may not see the difference right now, you’ll realize it soon enough.
Boarding schools (especially HADES, if that’s what you’re going for) look for maturity in candidates. You are applying to go live away from your family in a very rigorous accademic environment. Being “two years young” for your grade does not scream “I’m emotionally mature and capable of excelling at XYZ school!”.
Beyond grades and test scores, which only get you over the first of many hurdles, schools look at your teacher recs, interviews, and essays, to see that you are a mature and interesting person. Honestly, I know for a fact that my interviews and teacher recs are likely the biggest factor that got me accepted to a number of HADES schools. Giving yourself an extra year of HS when you will still graduate as one of the youngest students has little if any disadvantages. BS rarely accept unhooked 11th grades, if you decide to apply in that pool you’re likely setting yourself up for disappointment.
My vote is to take the previously mentioned advice and apply as a repeat 10th. It will give you extremely higher chances at almost any school. Unless you can give us a really good reason why you don’t want to, that is likely the advice you’ll continue to hear.