Sitting around the table during a family meal is very important. Even when the child is eating fast and say he is not hungry any more, ask him to sit until the end of the meal. Something, when the child will continue to sit around the table, you will see that he continues to eat and the reason for asking to leave the table, was to play and not because he is not hungry.
Yes, if he finishes eating fast, insist of him staying with the family and not getting up. Important to know that a big part of the family meal time is engaging in conversation and listening to each other. So even if your child is not eating anymore, ask him to stay. The child will learn a lot by looking at his parents and sibling eating, talking, communicating and will try to imitate them in the future.
How long should the child sit at a meal? answer: 20 minutes. That the recommended time for a child age 3 years old and older to engage in a meal, even if he chooses not to eat the whole time.