I think my son's clarinet teacher has this right. If a pupil plays something really badly she will say, as you do, "I think you can do better than that - try again." But if it's just as bad the second time she will say, "That needs more work at home" in a tone that brooks no argument, and move on to something else.
I don't think kids respond well to being told off. They know quite well when they haven't practised, and if they've had a busy week they just feel resentful if you get cross. At the end of the day only they can decide whether or not to practise, and that's more likely to happen if you notice when they have worked on something, and praise them for it. The carrot is much better than the stick here, I think.
Oh good, glad you think so. I too suggest they carry on practising it at home if it doesn't come right after a couple of goes in the lesson. They seem to get the message at that point.
Yes I think you're right about telling them off for not practising - what's the point? If they want to practise they will, and vice versa. I think it's better to probe a bit and find out why they're not practising and then try and help them come up with solutions. This week I realised a formerly very enthusiastic pupil had slacked right off with her practice. We seemed to have reached a sort of deadlock and I asked her if she wanted to give up and the response was 'no! I love my violin lessons!' I responded with: 'well that's great but you do need to keep progressing, and if you don't practise you won't progress' etc and then asked what she doesn't like about practising.
It turned out how mother tells her she has to do half an hour a day and hovers about listening and making negative comments. No wonder the poor girl isn't enjoying it! She told me she'd much rather pick up the violin for 10 minutes here and there, maybe a couple of times a day (she keeps it on a stand so it's easy to get at). So we've come up with a new strategy: I'm going to call the mum and ask her to keep away from practice apart from some casual listening and occasional positive remarks about the good bits and no negative remarks about the dodgy bits.
Also, I told her (the child) not to have a fixed half hour regime, but practise until she feels she has improved the things she's working on. If she can do that in five minutes, great! If it takes longer, so be it. Every week I'm going to record her and we can compare recordings; when she makes some really good ones she can collect them and then make a cd to give to grannies/sell at school fundraising events. She brightened up hugely and sent me an email later that day to tell me she'd been practising loads since she got home from school! I know it's early days, but fingers crossed...
So in this case some honest communication and a strategy of no telling off seems hopefully to have turned things around.