Complex sentence: It was founded in 1876 by five Sisters of Mercy as a boarding school for girls across the South; in 1959 it became coeducational and closed boarding school operations in 1963.
Split into simpler sentences: It was founded in 1876 by five Sisters of Mercy as a boarding school for girls across the South. In 1959, it became coeducational and closed boarding school operations in 1963.