Complex sentence: Adams decided that he preferred teaching so in 1848 he returned to teaching this time at the Boylston School in Boston, in 1860 Adams was promoted to the position of master of the Boylston School.
Split into simpler sentences: Adams decided that he preferred teaching so in 1848 he returned to teaching this time at the Boylston School in Boston. In 1860, Adams was promoted to the position of master of the Boylston School.