I ASKED A 17-year-old I know what he thought about Kwanzaa and he said, "That Jewish holiday?" Uh, no. Clearly, his high school hasn't embraced the multicultural thing and isn't teaching students about the 44-year-old Afrocentric holiday. But I don't knock his ignorance because the truth is that Kwanzaa has never caught on with the majority of black Americans. At the same time, though, it has grown in mainstream acceptance as evidenced by the Kwanzaa postal stamps and greeting cards.