Complex sentence: Kummer attended high school at Loomis Chaffee, a private boarding school in Windsor, Connecticut until 1974 and Yale University from 1974 to 1978.
Split into simpler sentences: Kummer attended high school at Loomis Chaffee, a private boarding school in Windsor, Connecticut. Graduating in 1974, he then went to Yale University from 1974 to 1978.