I'm an international Student and I find it hard expressing my achievements in a way that fit into American standards

Hello, I am in the 11th grade of Highschool in Germany, and because of how the school system here works, I am going to a school that the top third of students get in to, and am in the top 15% of my grade. However, since schools in my state don't offer AP classes, I haven't found a way to express this here in the chancing profile or on the common application. Additionally, I have always been very active at my school, participating in many activities such as teaching young students about media or chaperoning 5th graders on trips, but I don't know how to add things like this to extracurriculars. Any help on how I can properly assess where I stand in relation to other students would be great!