I started out RH, then at 6 started doing things LH out of boredom and for variety. This was tolerated by the school until 3rd grade where a teacher berated me for writing left handed and I stopped. In College I started doing LH stuff again as all my GF were LH but I am nowhere as good as I was when I was younger.

I think kids can learn to do both LH and RH equally well - and there are advantages to ambidexterity for input devices, writing, art, and sports. They just need encouragement.