What I've done is come up with a small cast list for the girls who go to an international school. Teenaged girls from all countries attend, with an associated boys school nearby. I've linked the various cars and other references in the cast list below, to keep things easy and clean.
Portia, from Germany. A strong competitor, loves track events, especially sprints where she can run full out.
Mercedes, from Germany. A very proper German girl, but can keep up Portia when she needs to. Has a rivalry with Martin Astin (see below). Has a younger sister who she loves dearly but thinks is very nerdy. Older brother is Baron Benjamin XXIII, the latest in a long line of Bens.
Opal, also from Germany. A more matronly lass than Portia, above.[link to car selection] Has a brother, Adam (see below).
"Mustang" Shelby, from the US. More tomboyish and rowdy than the other girls. Works out.[link to muscle car] Loves riding horses, thus her nickname. Despite her appearance, she can give Portia and Mercedes a challenge, especially in short sprints. Is seeing Martin Astin.
Arachne, from Canada. Much prefers the outdoors and cross-country running.
Agnese "the Lamb" Gallardo, from Italy. Soft spoken and shy. Capable of out running Mercedes and Portia, but isn't interested in the competition.
Clio, from France. Tends to fade into the background, but is reliable. Often joins Adam (below) on his cross-country runs.
Kaoru, from Japan. Also a fan of Initial D. Also into parkour, often getting into trouble with Lan (above)
Octavia, from the Czech Republic.
Samara, from Russia. Tries her best but has trouble keeping up with the others, especially Portia and Mercedes. Injury prone.
Barbara, from the US. Specifically, from Malibu, California.* Laid back.
Martin Astin, from England. A rival to Mercedes, especially in school performance. Is currently seeing "Mustang" Shelby (above). Wants to be a secret agent after university.
David Harleyson, from the US. The bad boy of the story. When he was younger, he was called "Fat Boy", but after bulking up over summer, he's known as "Iron"
Holden, from Australia. Enjoys long walks in the wilderness.
Frau Westphalia, from Germany. A teacher at the school, she dresses like a hippy. Enjoys brownies, which she never shares with her students.
Have an idea for other people at the school, either student or teacher? Want to submit a pic of one of the characters above? Let me know, either through my contact email or in the comments!