B.F.
I know with my kids they did the same thing and what i did was buy a mess mat to put under the high chair and everytime they tried to dump something or did dump something i pick it up put it back on the plate or bowl and set back in front of them. I kept doing this over and over and finally they just stopped. It might sound like alot of work but it will payoff in the end. the purpose of the mess mat was to prevent any food from getting on the floor. I did not put the food that fell off the high chair tray back to them. And for the suction bowls or plates they are a waste of money. My kids learned quick how to pull them off. Try a booster seat seat or something along them lines and have him sit at the table with you. Good luck.