If there is a proper healthy relationship between the parents and the child, there should be no need for locks on a door. And if the child is giving their parent cause for suspicion to look around their room then even more so there should not be any locks.
A parent who is wise, with a child who is sensible and does not have anything to hide, would agree that it is privacy enough just to close the bedroom door, and would certainly not go snooping around their child’s room to find incriminating evidence.