Table Manners (or Lack Thereof)

We have our work cut out for us trying to raise a respectful boy at the dinner table!  When Jackson wants food, he screams wildly.  He screams in an assertive, demanding kind of way.  He also throws his food and sippy cup when he is finished.  He casually drops it over the side of the high chair tray both at home and in restaurants.  Jesse and I just keep firmly saying "no" and picking it up, but he's behaved like this for months.  I don't know if there's something else we should be doing or if he'll just eventually learn. 

One of the things we're working on is using a spoon and fork.  Jack is very purposeful and works hard at getting the food on the spoon or fork.  Silverware can become an unintentional catapult, especially when given a bowl and spoon.  He tends to use one hand to pick the food up, then switch hands to actually put the food in his mouth.  His fine motor skills are improving, though.