Pupils aren't widgets. In a business setting if you make a faulty widget you either scrap it or recycle it. You can't do that with a pupil, and they generally only have one chance. I feel it is your duty to give them as much explanation as you can. If they ask for the admin password, don't just say they can't have it, give them all the reasons why they can't have it. With pupils "No" is often not an adequate answer.
Anyone who has young children, or who has raised children will know the constant questioning you get.