I once heard a story along the lines of the following:
A man brought his 7 or 8 year old son to meet the Chazon Ish. He wanted to show him what a masmid his son was. The Chazon Ish, after asking the boy a few learning questions, turned to the father and asked him if he taught his son mischief. The father responded with a confused look. The Chazon Ish turned to the boy, pointed to a chair, and told him to knock over the chair. The boy refused. The Chazon Ish encouraged the boy, but he could not bring himself to knock over the chair. The Chazon Ish turned to the father and told him he had failed to teach his son mischief.
The idea, as I understood it, was that the father should have taught the child how to have fun also.
Anyone know of a reliable source for this story, or a story to the same effect? If I have the wrong Gadol, I'll take the same story with a different name.