Complex sentence: In 1821, he entered the newly established St. Mary's College in Lebanon, where he became a favorite pupil of Rev. William Byrne, and was even made professor of mathematics at age fourteen.
Split into simpler sentences: In 1821, he entered the newly established St. Mary's College in Lebanon. At St. Mary's, he became a favorite pupil of Rev. William Byrne, and was even made professor of mathematics at age fourteen.