+1 on what John said.
I am finishing up my first bow that I have ever built and it is for my kids (just to give you an idea of my inexperience). I tillered it to be able to max out with the kids size arrows (28 pounds at around 22 inches). My 8 year old daughter is using just about all of the draw length and my 4 year old uses what he needs, probably about 15# or so. But he is getting one of own soon that will be a little shorter.