When I was in my 20s I was much tougher. Two of my former students (both in their 40s now!!!) have joked with me recently about times I sent them home, one time each, for not practicing.
On both occasions I told them: "Come back next week when you have practiced."
And both told me they are very glad I did it. It taught them a lesson.
But these days I *try* to make my points more subtly. Two days ago, I think, a six year-old told me that he didn't want to do what I told him to do first. All my students use a keyboard chart, mine, and they have to play through one piece without it, saying every note name. It is my way of testing to make sure that they are absorbing the note names. I tell them that the chart is "training wheels" and we have to get rid of those "training wheels" as soon as possible.
So while I am working ahead, with the chart, I review every page, one by one, from the beginning, with OUT the chart and with counting. I then push to "catch up" to the front of the book, which I am creating in each lesson with my own materials, until all old pages have been covered, note reading is solid, counting is solid.
So when the six year-old said he didn't want to do the page with the notes, as I asked him to, and his mother (part of the lesson) said she hasn't been doing it because he "resists", I told him:
"You don't have to do the notes if you don't want to. But you will have to work with another teacher."
I smiled. But I was totally serious!
Some things are not negotiable. Some things CAN'T be negotiable, and if we don't hold our ground now, we don't have a chance of teaching in a productive way, ever.