There are so many different methods of practicing an instrument.
Many teachers focus on repetition while others prefer to search for the musical freedom and expressiveness of the student. Some methods disagree with the practice of scales and patterns; others base all the practice routine on them.
In all this sea of ideas on how to approach practice effectively there is, without any doubt, one common ground, where all methods meet:
Any practice routine must be consistent, organized and must evaluate progress.
If you want to make your practice time worth its time, I strongly suggest using this workbook:
That will help them organize their practice routine and keep a record of their progress and achievements (also their weaknesses)
I've been using this system for more than 3 years now with all my students, and it makes a big difference in their consistency when comes to practicing their instrument.