You have a low chance of acceptance based on the fact of its competitive nature as well as the lack of success at your school for tippy-top acceptances. However, it is worth a shot in RD. Your ECs and gpa are fine/impressive and put you in the running, but rigor really matters. What courses have you taken compared to what has been offered at your school? Are you in the highest level of courses across most if not all of the core subjects? What are the hardest APs the school offers and have you or willyou be taking them? A school like Harvard expects you to challenge yourself across disciplines , considering what is available at your school.