Complex sentence: During the early 1990s, the high school went from being a parish high school to a diocesan high school, separating completely from the now-defunct St. Mary Elementary School (K-8).
Split into simpler sentences: During the early 1990s, the high school went from being a parish high school to a diocesan high school. Separating completely from the no longer operational St. Mary Elementary School (K-8).