Overall 10th grade applicant acceptance rates are very similar to the 9th grade acceptance rates (there are less spots, but also a smaller applicant pool). However, the major difference within the applicant pool for 10th grade is you are competing with A LOT of students who are in their last year of Junior Boarding school (9th grade) and need a spot at one of the boarding schools for 10th-12th grade. These students already have a ton of boarding school counseling from their secondary schools offices and the junior boarding schools are incredibly good at vouching for their students to get into their first or second choice schools. Essentially, all the Junior boarding school applicants NEED a boarding school for 10th grade and they cannot wait and reapply the year after (due to already having status as a boarder) thus they typically apply to several schools and put extensive effort into creating their apps with the help of their schools advisors. Overall, I really think thats the biggest difference within the applicant pools, and overall, unless your applying to a school like groton, which takes very few new 10th graders due to them having 8th grade-12th grade, I would say the application process and acceptance rates are usually very close to the 9th grade process.