Does having graduated HS a year ago mean that you'll be starting your second year of some kind of college in the Fall? If so, you should be warned that your academic responsibilities will soon start to noticeably ramp up. If you haven't done so already, I recommend that you read the hugely helpful
Think Before You Mentor thread from cover to cover.
Another difficult part of being a young mentor is developing adult relationships with the students and with other mentors. In this case, you'll have an important advantage over folks attempting to mentor the same teams they were on as students: instead of trying to redefine your old relationships to fit your new role as mentor, you'll have the chance to develop new ones.