For children 1 and 2, they went to piano lessons from when they learned to read, up until they started hating it and asked not to go anymore, which was right about the age where your son is. But, we told them they could quit lessons IF and ONLY IF they continued practicing own on a schedule. They agreed to this since it got them out of the lessons. They went through the Hymn book. My son (oldest) was called at 14 to be the Priesthood Opening Exercises pianist. My daughter played in seminary and for young women.

With children 3 and 4, they wanted to give up much earlier. We still expected them to go up until starting junior high, but we were probably tired of the struggle, plus they were very different personalities and really didn't show as much aptitude. We let them out of piano with the promise they would be in Jr. High band.

Now, several years later, my oldest two play well, although my son has the best ability. Both LOVE playing, and do so all the time on their own. Children 3 and 4 can't play well at all--they can play the simplified versions of the hymns, and that's it. #3 plays clarinet, and she's pretty good at that. #4 did percussion in band, but she's now going to focus on choir.

I don't know that forcing anything with any of them would have done any good. Once they get to their teens, they either have to want it for themselves, or it's not worth it.