I’ve just bought a used Xbox 360 S and parental controls were enabled. How do I turn them off?

Hi, I'm Luis a Xbox user just like you. Thanks for reaching out us here. Unfortunately not even a factory reset would get rid of the parental control settings. You need to contact that previously owned the console to have it unlocked

You cannot change the age but you can turn off Parental Controls. See:
support.xbox.com/.../parental-control for the steps (that document tells you how to turn them on but it is the same steps for turning them off... You can see the Off option in the image).

Hey there Saucer!

I suggest checking out our guild on how to
set parental controls for Xbox 360 and Xbox Live. It shows you how to enable and disable parental controls. ^_^

support.xbox.com/.../parental-control

Just go in there and turn it off, save and exit.

Hi, you can enable parental controls in your or yours son´s account. With it enable you can disable purchases over xbox.com or you console.

Just folow these steps :

support.xbox.com/.../xbox-live-parental-control