After
Pre-growth spurt they go into an "eating frenzy", where they store the necessary calories and such in order for the body to burn during the work period of adding a few inches to height and such. Sleep is often affected because the body is gearing up.
You only grow when you're sleeping, as when you are sleeping, it's the only time the body releases the necessary hormones that trigger growth.
*HUGS*
Sonya =P