What are my chances to get into a BS?

I’m currently a 10th grade brazilian student. I found out about Boarding Schools on May, and I’m really interested in applying to them. Although I’m not sure if I’ll be accepted into one.
My grades are mostly higher than 80%, considering the education in Brazil I think it’s great. But I don’t have many extracurriculars, I love to play volleyball but I didn’t have a chance to compete seriosly because there’ve always been better people than me in my class. I also pratice argumentative essays because it’s a requirement if you want to attend a college in Brazil, and I’m praised by my teachers for these essays, but I just competed one time last year on behalf of my school against the schools in the same network as mine in my state, and I won the third place.
I don’t consider myself a fluent in English but I’ve been taking an English course for the past two years and I finish it by the end of the year. In addition to the English course I’m studying by myself every day to improve my English and I’m also studying to take the SSAT, and I scored 2005 in my practice test, is it good?.
I intend to try my chance applying to some top BS, but also BS with a higher acceptance rate. It’s my dream to attend one of these schools but sometimes I’m afraid of not being accepted. What do you think?
Ps. I’ll also have to apply for financial aid.
ps2. Sorry for any mistakes I might have made.

If you apply to boarding schools that are a good match for you, you increase the probability that you will be accepted.

Don’t count on getting any particular score on the SSAT until you actually take the SSAT. Realize that with Covid-19, the SSAT may be a non-issue.

I don’t know anything about the Brazilian education system, so I have no idea if 80% really is “great”. It is very important that at least one of your letters of recommendation put this in better context.

(In my school district, an 80% won’t cut it to get into Honor Society; you’d barely make Honor Roll. But then again, my school district is a mess… )

Do look at a lot of schools - there are many lesser known schools that might be a great fit. Look more at the profile of the school than the acceptance rate.