Complex sentence: Obama returned to Honolulu in 1971 to live with his maternal grandparents, Madelyn and Stanley Dunham, and with the aid of a scholarship attended Punahou School, a private college preparatory school, from fifth grade until his graduation from high school in 1979.
Split into simpler sentences: Obama returned to Honolulu in 1971 to live with his maternal grandparents, Madelyn and Stanley Dunham. He attended Punahou School--a private college preparatory school--with the aid of a scholarship from fifth grade until his graduation from high school in 1979.