I found this article written by a fellow music teacher from The Music Parents Guide blog really insightful, it may help you (my parents, and other parents of children in music lessons) in the trenches at home.

Who Actually Quits Musical Instrument Instruction — Children or Their Parents?

I quit. Many times. My mom had a lot on her plate, and yelling at me about piano was much harder for her than just letting me quit.
But since I’m a musician and have been since the age of 8, I never gave up. After going through a few teachers by the age of 11, I taught myself how to play. When I finally “grew up” a bit by the time I was a junior in high school, and was frustrated from a lack of progress at the piano in classical training (I was already on my way in the pop music dept., thanks to Burt Bacharach et al.) I went to the best teacher around, who taught many kids in my small New England town. When Mrs. Westman introduced me to the world of Mozart and Beethoven, there was no turning back.

I got this from someone, somewhere, so it’s not my own, but it’s a great thing for parents to try out when struggling to get their kids to practice:

“Find me 3 adults who say ‘I’m so glad my parents made me quit piano when I was a kid!’ and I’ll let you quit piano.” 🙂