I would say that the the responsibility of the psychologist (and all doctors) is to their patient, which in this case is the child. That does not necessarily mean that it is unethical to disclose what was said to the parents, as doing so may be in the best interest of the child.

However, there is a significant second order concern with violating confidentiality. In future instances, the child may be less willing to speak "in confidence" with a psychologist.