The parents should say something to the kid and make it clear that he/she belongs at the table.
Well, there’s a good way to make sure the kid hates Shabbos. Way to keep him on the derech.
It depends on the age of the child. For sure younger children should not be kept at the table. Try sitting at a table where people are speaking a language you don’t understand. That’s exactly what your child is going through. (Thank you Rabbi Noach Orlowek for that.)