D.C. Code § 38-1908

From and after 10 days following August 28, 1958, there shall be only one person in charge of the following departments in the public school system of the District of Columbia: Art, business education, English, foreign languages, guidance and placement, history, home economics, industrial arts, mathematics, military science and tactics, music, science, trade and industrial education, and health, physical education, athletics, and safety; except that in the case of persons reassigned pursuant to this section, nothing contained herein shall be construed to decrease the rate of compensation that any such person is receiving on the effective date of this section. If such person is placed in a lower salary class and the present salary of the incumbent falls between 2 step rates for the newly assigned class, he shall receive the higher of such rates. Whenever a department is established hereafter in the public school system of the District of Columbia there shall be but 1 person in charge of such department.