Applying to Harker as a Junior

I’m thinking of applying to Harker as a junior for next year. How many spaces are there for students by 11th grade, and do so many people apply for these spots that it’s extremely competitive to get in? Additionally, will they let a student send SAT/PSAT scores instead of SSAT/ISEE scores? Is it worth the effort to even apply if I don’t have stunning extracurriculars and not even a 4.0 (but 10+ AP classes by the end of sophomore year)?

I’m not sure if this is clear but I’d be applying to BE a junior – class of 2020 to be exact.