I've taught many thousands of piano lessons. Here are a few things worth knowing that your piano teacher might not share with you.
Many students never leave the beginner phase. Students need a lot experience in a very targeted range of music to leave the beginner phase convincingly. Many students choose to jump ahead of this range to work on more difficult pieces and end up not progressing at all.
Method books often drag out the learning process. Many teachers use method books to train students who are brand new to piano. While method books can be convenient, they may result in more lessons needed at the beginning stage of piano study.
Adults often learn faster than kids and generally need less lessons. Some students may see better results by waiting until they are adults to begin serious study of the piano. Adults generally have an easier time grasping difficult concepts and sustaining good practice habits.
Some students learn significantly faster than others. Students who learn to practice effectively can become advanced with relatively few lessons. Other students may require years of lessons to develop their skills.
Not every teacher works well with every student. For lessons to be productive, learning and teaching styles need to match up. A good teacher can generally accommodate a wide range of learning styles, but still might not be the best fit for every student.
Piano teachers disagree on a variety of topics. One teacher's favorite strategy might be useless to another. There are multiple paths to success when it comes to learning a musical instrument.
If you or your kids plan to study piano at some point, these things are worth keeping in mind.
Ultimately, it’s up to you to determine what you want from piano lessons and manage your expectations accordingly.