Complex sentence: Because literacy for blacks outside of religious instruction was discouraged at the time It is not known with certainty how Shiner learned to read and write, but historians have speculated that he may have learned from a small school at the Navy Yard run by white abolitionists.
Split into simpler sentences: Because literacy for blacks outside of religious instruction was discouraged at the time, it is not known with certainty how Shiner learned to read and write. Historians have speculated that he may have learned from a small school at the Navy Yard run by white abolitionists.