How does Zhao Meng teach his son to practice calligraphy?

Zhao Meng pays great attention to brushwork, and thinks that it takes 1,000 strokes to write magnificent words. When he teaches his son to write, he often stands quietly behind his son and suddenly pulls out the pen holder in his hand. If the pen tube can't be pulled out, he will laugh happily; If the pen tube is pulled out, he will naturally be very unhappy and will punish his son.