Our Dog is Stupid

For those of you who don't know, we have a 19 month old Boxer named Lucy. She is for the most part o good listener, and obeys well, and she cleans up the kids messes after there done eating, but she is stupid.(Sorry if you don't use that word, but there is no better way to say it.) For example, as soon as I turn my back Lucy will go up to SJ and take what ever food she has in her hand and eat it even though she knows she is not suppose to, SJ will come tell me what Lucy did and the dog heads for the back door because she knows I'm going to make her go out. She eats things she is not suppose to eat, and I'm not talking about the kids food, I'm talking about marbles and rocks. So about 15 minutes ago I was sitting here at the computer enjoying the quiet. The girls are sleeping, the boys are in the toy room watching cartoons, and Michael is out in the garage. Total silence. I hear the dog making that awful noise like she is going to throw up, I run out in the other room and yell NO LUCY GET OUT, but guess what it is to late, she threw up some grass and two rocks that she ate about a week ago. This is the second time that she has eaten rocks, and there not the rocks from outside there rocks that the kids play with, that you can buy at the store. Between the four kids and the Dog, the Dog is the worse one.