In accordance with the State budget, the Secretary may employ a staff and retain consultants. The Secretary shall appoint: any assistant secretary; any director of an institution; the superintendent of the youth centers; and the managing director, deputy director, and director of detention at the Baltimore City Juvenile Justice Center. An employee of the Department specified in subparagraph (i) of this paragraph: is in the executive service or management service of the State Personnel Management System; and serves at the pleasure of the Secretary. Each teacher who does not hold a certificate under Title 6, Subtitle 1 of the Education Article, principal, director of education, and supervisor of vocational education who is employed by an institution managed by the Department is in the management service of, or is a special appointment in, the State Personnel Management System. Unless otherwise provided by law, the Secretary shall appoint and remove all staff in accordance with the State Personnel and Pensions Article. Unless the Secretary grants express permission, an employee of the Department who is subject to subsection (b)(1) of this section may not engage in other employment while employed by the Department. The Secretary may not unreasonably withhold express permission to engage in other employment. If the Secretary grants permission to engage in other employment, the employee shall disclose to the Secretary the source and amount of all income earned from that other employment. The appointment or removal of staff of a unit in the Department is subject to the approval of the Secretary. The Secretary may delegate the power of approval established under paragraph (1) of this subsection to the head of the unit. The Department shall: adopt a code of conduct for staff of the Department; and require each private agency under contract with the Department to adopt a code of conduct for its staff that is in substantial compliance with the code of conduct for staff of the Department.