In 1952, upon Tobin's retirement, the school named teacher Charles W. Cook (class of 1938), as its fourth headmaster. Under his 36-year leadership, the Browning School expanded rapidly. After a lengthy fundraising drive, the school bought the adjoining carriage house and rebuilt it, and the new building opened in 1960. The school's expansion continued in 1967, with the building of a larger gymnasium on the roof and, in the late 1970s, with the acquisition of an interest in the building next door.