result: after a big scolding, I left her alone to practise the scale during the whole lesson time (1 hour).
Any other idea what I could have done ?
Punishing is a really stupid thing
It just teach a child that he must do something because otherwise he will be punished instead of teaching to do something beause of passion, love or out of resposabilities
By punishing you never teach justice, you can't teach a 11 years old kid not to smoke by punishing him if you find out that he has smoked, you can just teach him the right thing to do explaining the health risks linked with smoking and explaining him that it's because you love him that you don't want him to ruin his health
Of course, you can threat a kid telling him that if he doesn't study his scales you would punish him, but in this way he would just practice out of fear not because of love, passione or really understanding... and if I were you I would prefer not to have any students at all instead of having a lot of students that keep taking lessons from me just out of fear
Why don't you try the reverse process instead?
Instead of punish her if she doesn't study her scales, why don't you "reweard" her when she study her scale well?
It's clear that she needs some motivation and your attitude and your lessons are not giving her any
The strongest motivation of all would be to feel how fantastic and pleasant is to play well making your teacher proud of you
Surely any kind of punishing that involve piano playing is just absurd !!
Do you want them to think that playing piano is something wonderful and useful or just a way to punish someone?
It's just like math
You can't punish a student that didn't study his math by making him study more math
He rightly, will think that it true that math is useless if it is used as a way of punish instead of being used for its real purposes
If she really loves piano, then a more intelligent punishment, instead of involving piano playing, would be "not involving piano playing"
Yes, if she doesn't study you can tell her that you don't want her at your next lesson unless she doesn't know her scale perfectly
Then she would understand how much she love piano and how important are your lessons for her and will be compelled to really study for a real strong motivation
If even after that she doesn't study her scale it simply means that she doesn't give a damn about your lessons
Mind you, not the piano, you and your lesson!!
Daniel