Should I report a client who reveals a history of sexual abusing a child?

Hi, I am a student counselor. If a client tells me that they sexually abused a child in the past, but not currently and does not want to in the future does that have to be reported? Does it change if the child is under or over 18 at the time the counselor is told? I want to make sure they are engaged in a therapeutic process that includes both informed choice as well as having the dignity of risk. I am aware this may change from state to state, wondering what is usual. Thank you!