My Son and I regularly shoot together for score and he often "beats" me using the following formula.
We began by shooting for score and recording our scores. Next time out he got the points difference between our last scores. I keep my running average score and his and each time we shoot together he gets the difference. Using this method he often beats me, as my scores stay pretty constant and his are getting better and better as he gets older.
The only thing he gives me a hard time about is that he doesn't get a whole lot of points anymore as he is getting pretty good ;~)
Keeping it fun keeps em interested!
This of course works for any adult/youth situation or just about any other where the shooters are of different abilities.