Parents and students often ask, "How many times do I repeat a section, phrase, group of measures, or other music element(s) when practicing? How long should I (my son/daughter) practice?"
The Role Of Repetition In Practice
My standard reply is that It is not the quantity of repetition, but the quality of repetition that is important. Students should strive to develop focused concentration during practice rather than on merely repeating something "X" number of times.
This is indeed a good and critical question as it relates to practice habits and how best to practice. I spend much of lesson time focused on just this topic, even though it may not seem like it, and so as a practical matter the question answers itself by observing how I work with students during the lesson.
The short answer is, "It is not the quantity but the quality of repetition". I actually prefer to use the phrase "focused concentration" rather than repetition, and the reason for this is that repetition in and of itself can become mindless and counterproductive. What is really required is active listening while practicing, self-critique in real time, and immediate intervention when things don't go right or when things just aren't "good enough". This is my approach to teaching and practicing and is almost an art in itself that I have developed for myself over many years and which a student can only develop over time.
Parents who sit in on my lessons will observe that I don't just "cover or explain" material that the student is required to learn and practice on his/her own for the next lesson, but that I actively engage in a real "practice" session with the student. It is important for each student to take this process home so they can begin to follow the lesson example of how to practice. In fact, this is a critical part of the lesson.
I can't stress the importance of good practice habits too much. The greatest time killer and inefficiency in learning piano is developing bad habits such as ignoring "lessons learned" during the lesson. Such bad habits will always result in learning a piece "the wrong way", whether it be rhythm, fingering, notes, or whatever. When this happens, we need to take time to "unlearn" before we can get it right, hence the inefficiency.
For young learners, a certain amount of such required "unlearning" is inevitable, and this is why a two lesson per week schedule is always preferable. More frequent and consistent reinforcement of the "lessons learned" provides a hedge of protection against the development of bad habits, helps to minimize the hidden cost of time needed to "unlearn", and actually speeds up the learning process.