Sec. 13. All hearings held in proceedings under this chapter shall be held in closed court without admittance of any person other than:
(1) essential officers of the court;
(2) the parties;
(3) witnesses;
(4) counsel;
(5) persons who have not previously consented to the adoption but are required to consent to the adoption; and
(6) representatives of the agencies present to perform their official duties.