I’m a rising sophomore at a private, parochial high school, and I’m applying to a few HADES schools for the 2019-2020 academic year. If I were to apply to be admitted as a sophomore rather than a junior (i.e repeat a year), would my chances for admission increase? The school I have particularly in mind is Exeter, and I read that they would generally admit one hundred students into their sophomore class, but only 20 for their junior and senior classes; however, I am uncertain on whether or not the number of applications received would impact insofar the number of new admits.
Your best chance of admission at any of those schools based on numbers is with the freshman class. Admissions numbers reduce drastically with each upper class. Yes, applications decrease as well but your (anyone’s) chances of admission to those five schools is very low especially to the upper classes.
There are way more than five excellent boarding schools; that acronym doesn’t begin to include all of them. Your best chance for admission is not only to apply to more of them but also to those that are a good feel and fit for you personally and where your stats put you well above the average matriculant for that school. The five schools in that acronym are very different from each other; you might have a hard time making a case that each of those very different places is a perfect fit for you.
Start by making a list of what you think a boarding school will give you that your current school does not. Also, use boardingschoolreview.com to create a list of schools that meet your general criteria (size, location, student-teacher ratio, etc.) and take a look at what some of the experienced posters here consider hidden gems:
Also, if you do some research here, there are many threads discussing why it is better to enter boarding school with the lowest class possible–which boil down to more time to reap the education, social, and college prep benefits of the school. The downside, of course, is the increased cost for attending any additional year.
Good luck to you, but please toss that meaningless acronym and do a search that will produce the best options for YOU. 
ETA: I see from your other thread that you need FA and your current stats do not make you a standout for Exeter. Please understand that generous FA is not limited to the schools with the largest endowments. Apply to schools where your application is (very) competitive. Schools use their FA budgets to attract and support those applicants who are somehow “shiny” for their communities. You need to find that match; don’t focus on the size of the FA budget. A huge FA budget is irrelevant if it doesn’t apply to you.
Thank you for your response,
I have been looking into additional schools and have found some that I like. I understand that I’m not a particularly strong candidate, especially in terms of GPA, but I hope to remedy that through other things such as test scores, extracurriculars, and hopefully through my interview. I have also been looking into schools with a needs-blind admission policy, since I will need financial aid regardless of which school I choose.
The only school that still claims to be need-blind is Andover where you have about the same chance of admission as Exeter. It’s certainly OK to apply to these schools, but make sure you also apply to others you have a better shot at.