Table manners are an equally important but separate issue. For children to develop good table manners they must be in the habit of sitting at the table at mealtime, eating with the family, and being exposed to the good table manners of adults and older children.
Encourage your children to eat with their mouths closed. Next, see they sit up straight and avoid leaning on the table as they eat. Next, encourage eating with a spoon instead of fingers, and gradually encourage them to eat most foods with a fork, encourage them to hold the fork in their fingers instead of their fist. They should begin to learn the proper use of a knife. By the time they are six or seven, include learning such manners as asking that things be passed instead of grabbing for things, and not whistling or singing at the table. It is not desirable mealtime become a continuing hassle or series of reprimands. You want your child's table manners to gradually improve. Since children do not learn the first or second time (frequently not even the ninth or tenth), continuing and gentle reminders are needed.
What happens if insistence does not lead to better behavior? First, keep trying; insist more firmly; perhaps send your child away from the table, and then allow him to return in a few minutes. Above all, remember the central reason for sitting down at the table is to eat. Good table manners are related but separate. Keep your main focus on eating habits and patterns. Place secondary emphasis on table manners. In time, both develop.