Complex sentence: During his childhood, St. Clair lived in a mixed neighborhood, and while his knowledge of race and prejudice was vague, at least one of his fights occurred when he was insulted about the color of his skin.
Split into simpler sentences: During his childhood, St. Clair lived in a mixed neighborhood. He recalled that his understanding of race and prejudice was vague, but at least one of his fights occurred when he was insulted about the color of his skin.