One of my neighbors came over and helped me tweak my bow last night. He told me about a friend of his who wanted to get his wife to draw more weight on her bow.
Everytime she'd go inside for water, or was distracted from their bow practice long enough, he would tweak her bow up ever so slightly on the amount of weight she drew.

He took her, by very slight incriments, from 50-65 lb. draw before he ever told her anything. Of course he got smacked a good one when he told her.
All turned out well in the end though. She was happy with what he did.

This could work on kids too. If they are thinking they can't pull more....