This comes up a lot when we talk about film, and think most of it comes down to the quality of the movie. Poorly drawn movies tend to depend on poorly drawn characters. And poorly drawn black characters almost always descend into stereotype and cartoon. Not that I'm an expert on Teen Movies, but I can't really think of another one--pre-Clueless--that had African-American kids in strong supporting roles, looking like we look, which is to say, like human beings.
Here's Siskel & Ebert offering their take back in the day.
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