To answer the posters questions: I agree with the above.
Schools: Apply to a good range of schools as there are tons of talented applicants applying to a select number of schools with limited spots.
Visit: I encourage visiting schools when in session, if you can. And then again for revisit days if accepted. (If either of these are not options, attend as many online things and talk to as many people as possible to get a better sense of the school and culture.)Sometimes the schools you think you love either by reputation or slick marketing are not the best fits.
Application Timing: It does not matter when you get your materials in as long as they are in by the due date. Many schools do not even start reviewing until after that date.
SSAT: SSAT is a just one more piece of information. Schools use it to see that you can do the work. Sometimes they do not take students with very high scores just as they sometimes take students with lower scores. It really depends on the whole application and what the admissions’ teams sees that you can offer to the overall community.
ECs: Do Ecs that matter to you. too many kids think they need a laundry list of items. Schools will care about what you bring to their community and that your interest align with their offerings. So passion, dedication and success. Exploration is find too, you are still young.
Interviews: See these are a fun conversation to connect with someone. All but one of my daughters interviews were great. Interviewers are not trying to trick you; they want to get to know you.
Essays: Allow time for the essays. I cannot stress this enough. While you can reuse some, some questions differ slightly and have different word/character counts (pay attention to this not just on the form but also on the site you are loading onto - they are not always the same). My daughter wrote or edited a range of 54 short answer (sentences) and varying length essays for 13 schools.
Good luck - BS is amazing for the right person. Regardless of your decision or the outcome you will learn a lot about yourself in the process