. In counties with a population of 500,000 or more, the county board of supervisors shall provide the court with the services necessary for investigating and supervising cases under this chapter by operating a children's court center under the supervision of a director who is appointed as provided in s. 46.21 (1m) (a). Except as otherwise provided in this subsection, the director is the chief administrative officer of the center and of the intake and probation sections and juvenile detention facilities of the center. The director is responsible for managing the personnel of, and administering the services of, the sections and the juvenile detention facilities, and for supervising operation of the physical plant and maintenance and improvement of the buildings and grounds of the center.