Complex sentence: The new law closed all schools for mulattos in that city, as in Virginia (and other Southern states), after the Nat Turner Rebellion of 1831, and prior to Reconstruction after the Civil War, it was unlawful to educate non-whites.
Split into simpler sentences: The new law closed all schools for mulattos in that city, as had happened in Virginia (and other Southern states) after the Nat Turner Rebellion of 1831. Prior to Reconstruction after the Civil War, it was made unlawful to educate non-whites.