Complex sentence: After Mr. Tierney retired in 2005, he was briefly succeeded by the school's first female headmistress, Terry Sweeney, as acting principal, she was succeeded by current principal, Paul Brannigan.
Split into simpler sentences: After Mr. Tierney retired in 2005, he was briefly succeeded by the school's first female headmistress, Terry Sweeney, as acting principal. She was succeeded by current principal, Paul Brannigan.