In 1929, Seattle College (later Seattle University), officially separated from Seattle College High School and returned to the Broadway and Madison campus. In 1933, the high school was renamed Seattle Preparatory School.
The opening of the school year in 1937 saw the beginning of the "Christy" McDonnell era at Seattle Prep. Fr. McDonnell, SJ served as principal, president and rector until 1956 and, with his commanding presence and charisma, is deservedly recognized as one of the great leaders in Prep's long history. His picture now hangs in McDonnell Hall, near the portrait of another extraordinary Prep leader, Fr. Thomas Healy, SJ.
The structural change in the 1970s - three years of studies at Prep (MRC Form 1) followed by three years of studies at Seattle University (MRC Form 2) - was altered in the early 1980's so that students could stay at Prep for senior year instead of being required to "commence" to Seattle University after Junior year. (This adjustment was made because, almost immediately after the creation of Matteo Ricci program, Prep's freshman enrollment dropped dramatically.) The MRC option remained available for Prep students for 40 years after its creation.