We are constantly nagging our DS9 (nearly 10) to practice his violin. He eventually does 10 minutes the day before his lesson after we've nagged him all week. It's just so tedious and I've now told him straight out that he's free to stop lessons at any time, but he's not free to have lessons and not practice. He's stormed off in a huff with his violin flung on the sofa. He has spent two years learning and isn't remotely ready for grade 1. I don't mind the grades per se, but he just doesn't seem interested and is making no progress. What's reasonable here??