Screen time won’t allow me to change the passcode on my sons iPad?

I set up a screentime passcode in my sons iPad and can’t remember it! I have followed the instructions to change it which led me through the process and now doesn’t recognise the new password and keeps asking me for the Apple ID which I provide and then the old passcode! Which kind of defeats the purpose as I don’t remember it? I don’t want to wipe it as he has so many pics and videos on it! I jutst want to remove screentime!