Complex sentence: In 1876, Roe was appointed headmaster of the Brisbane Grammar School (founded 1868) and had only a small number of pupils, but during Roe's reign of 33 years he built up a great public school.
Split into simpler sentences: In 1876, Roe was appointed headmaster of the Brisbane Grammar School. This school had been founded in 1868 and had only a small number of pupils, but during Roe's reign of 33 years he gave it the standing of a great public school.