Shoes that Stretch as you Grow

I totally love this idea from my other daughter, probably because I spend millions of dollars a year on the endless need of properly sized shoes for my kids.  You could either have inserts that you put into the shoe that you took out as the kid grew sizes (probably only do 2-3 per shoe).  Or you could use a spacer in the middle of the shoe that you could take out or put in as needed.