Complex sentence: Miami Norland opened its doors to students in 1958 as an all-white school, taking in 350 students, including students in grades 7-12; once Norland Junior High School opened across the street, grades 7-9 moved there.
Split into simpler sentences: Miami Norland opened its doors to students in 1958 taking in three hundred fifty students which included students in grades 7-12, as an all-white school. Once Norland Junior High School opened across the street, grades 7-9 moved there.