Seventy of them in various countries offer a wide variety of nationalities to host families and schools.
Specifics are here.
Partners may also attend AYA January or August orientations, national or local meetings. Independent admissions - Students that are from countries where AYA does not currently have a partner can apply through AYA's Independent admissions program. These students must find their own host family and have an acceptance letter from a local high school. The same application procedures apply.