T.- I read this last week on an email I got, I hope it helps-
Tool: Right wrongs together
Age: 12 to 24 months
How it works: There's a difference between a baby who playfully throws her bowl to the floor and a young toddler who knows she's creating a mess for Mommy or Daddy to clean up.
That turning point happens when your child becomes capable of knowing when she's doing something she's not supposed to, often around her first birthday. "When she looks at you with that glint in her eye and then drops the peas, you know it's time to do something." says expert Madelyn Swift. What you do, says Swift, is start teaching the concept of taking responsibility for her actions.
Real-life application: Your toddler's made a mess under her highchair. Lift her up, set her on the floor, and ask her to hand you some peas so she's "helping" you take care of it. Talk to her about what you're doing: "Okay, we made a mess with the peas so we have to clean it up." Then put her back in her chair and give her something else to eat, or end the meal.
I hope this helps, I know that it won't be as feasable to try at daycare. I've worked in a daycare before, and I don't know how big your son's daycare is, but we watched about 16 kids and there was only 2 of us, and it's my experience that mealtimes are the most dreaded times of the day. We have a boy there that is the same age as your son, but he only throws his plate when he's finished eating, but we have to move his highchair to where he can't eat others' food. I know that's not a way of teaching him not to do it, but it's an immediate fix for daycare. Also, if he is still in his highchair, you might consider moving him to the table for a meal to see if he still throws his plate to the floor. Sometimes just seeing a whole table in front of him instead of just a little tray will make them forget that they used to throw things off of their chair, because there isn't anywhere to throw the plate now that there is a table in front of them (although he may recognize that he can still throw it to the side, it might be worth a try). I hope this helps