Post grad year HELP

<p>I am a senior who is looking to do a post graduate year at a boarding school. I struggled my freshman year of high school and am looking to redeem my self in a sense. I am looking to apply at Hotchkiss (I have a friend that attends), Phillips Academy Andover (I am a competitive swimmer and Andover has one of the best in New England) , and Avon Old Farms (much closer to home). What are some of the things that I should know/keep in mind when applying? What are the acceptance rates for a post graduate year? Thank you for taking time to read this.</p>