I think it is most important for a teacher to play the pieces and studies that are being played by the student.
Scales played in the correct musical way are very exciting and rewarding.
Yes indeed I have gained a lot out of playing scales and etudes.
You cannot prepare enough for anything.
By the time I got to the Paris Conservatoire I was very good at the scales and arpeggios.
Never just run through a study because you happen to be familiar with it, but use it to see what you can get from it on this new day which has been granted you.