You have brought up an important facet of teaching! If the parent(s) are supportive and help guide the student’s practice sessions constructively during the week between lessons, that student will progress at a much faster rate than someone without this advantage. However, I have met parents who were so unreasonable in their expectations that it caused their talented child to quit playing. At the other end of the spectrum, I have run into parents who were so lax about whether their child practiced or even got to their lessons, that it seriously hampered the student’s development. Then there are the ones who force their reluctant and unhappy kid to study music for all the wrong reasons. I try to rise above it and not let it affect the lessons, but if I have a student who really does not want to be there and has no gift for music, then I gently point the parents in the direction of another field that might suit their child better.