size - how can you tell its normal?

Question
my year-old sheltie seems both shorter in height and smaller in length than most shelies I've seen.
I got him from a breeder, where both of his parents were present, and his parents were normal size shelties.
do they continue to grow after the 1 year mark? or this it?

also, I read that their coats don't reach their beautiful fullness until age 2.  is this correct?  

Answer
Donna,

The coat question is easy: by age 2 is true.

The height question is a challenge.  There is a bottom end and a top end for Shelties.  Many recent champions have tended toward the bigger end.  The "official" description is:
"The Shetland Sheepdog should stand between 13 and 16 inches at the shoulder. Note: Height is determined by a line perpendicular to the ground from the top of the shoulder blades, the dog standing naturally, with forelegs parallel to line of measurement."  source: www.akc.org

I hope that helps!

Dave