@mjames, @Outin and @visitor:
The attitude towards these type of students in this thread is pissing me off. For of all you started playing piano voluntarily (so those who were forced by parents when they were kids don't count), what motivated you to want to learn it in the first place? Were you drawn by particular piece of music? What was it?
I apologise that you feel this way; however, I have not reached this point of view by lack of reasoning. To the contrary, this standpoint comes after being: 1) a student beginner, learning how to play; 2) a student studying at ‘advance’ levels; 3) as teacher, teaching students at both those levels.
Perspective is vital; the more points of view we take note from, the more we begin to see an overall picture of the state of affairs.
The true difference between an advanced level learner and a beginner is the advanced level learner has taken time (however long) to make connections in the source material; the beginner is yet to do so. This time could consist of one year, or it could take thirty; the result is still the same, connections.
One can skip the basics and jump right into the ‘challenging’ repertoire; but we owe it to our audience to do a good job of it, whoever that maybe (ourselves or paying ). Playing for one’s own enjoyment is no excuse; however, it does give a suitable alibi for doing it all wrong.
It's all very understandable though: Practically all piano teachers have started their own learning as young children. They really cannot understand how different the premises are when someone start as a mature adult. They tend to apply the same learning principles to their adult students that worked for them and work for majority of children (usually because the parents force them to practice).
Learning, is learning; age is irrelevant. The overall majority of adults are incapable of mutable concepts; that is allowing new information to replace old. The result is: learners who come for lessons with preconceptions being the single and most difficult group to teach; progress is hampered from the outset because of this.
If it fails they explain it with the lack of discipline, arrogance and ego problems of the student. And the occasional cases where their method does work with adults just reinforce their perception.
Echo chambers are never a good thing; also, we have to acknowledge there are teachers who utilise flaw methodologies. However, this cannot change the fact that most adults have a fully formed ego and perception of self, and self-worth which leads them to the conclusion: “I do not need to do [X], [Y] or [Z]” which in itself is the definition of being arrogant: “having or revealing an exaggerated sense of one's own importance or abilities.” (Cambridge University Press, 2016). Expecting to play any piece of Baroque, Classical or Romantic repertoire without being able play a scale in the piece’s home-key is arrogant. To expect to do so at the level of a seasoned pianist in less time would also qualify.
It has also became clear to me that many teachers have plenty of good practical teaching skills but very little knowledge of modern pedagogical research.
Please elaborate.
So they don't have so many tools to assess their methods analytically when the students don't respond to them the way expected.
I cannot speak for other teachers, but I can certainly say I can discern the problem of a student’s lack of success after one week’s solo study. Though we like to believe we are all unique, unfortunately we are not; there are many ‘tell-tale’ symptoms that even after 10 seconds with a student, I can discern what the problem is. However, you have not accounted for the responsibility of the student to carry out the tasks as instructed:
“A doctor prescribes a course of medication. The patient takes the a few doses and starts to feel better then stops. After a few weeks the affliction returns, they take the medication, but this time to no effect. The patient returns to the doctor exclaiming that the medication did not work. The doctor then prescribes a different medication and the cycle continues.”
Though, greatly simplified, the concept is the same; students will do as they please, we can only hope it includes what we asked, exactly as we asked them to do it.
Since learning to play is very demanding and time consuming and not very well suited with an average adult lifestyle, adult students would require a more tailored reflective approach and more support than most kids. Few teachers seem to be well equipped for this.
It also seems to be impossible for many teachers to understand how to set goals with an adult student.
Again, we can set goals, however the adult will do what they please; we can only hope. Unless the task we set is directly linked (that is, the task they desire itself), most adults I have encountered respond with: “I don’t see the point”, to which I explain, and they ignore my advise and go about their business anyway. Very few listen and respond with: “Oh … I see”. From what I have encountered, they go along with what I set with half-effort almost waiting for something to happen, not realising it will not until they do it.
Longest I have witnessed is, four years asking a person to practice while counting the measures out loud. Every week they would not do it , until one week (four years later) they did and everything clicked into place; they exclaimed “Wow … it’s so much easier when you count”; I just smiled back politely.
How many adults (or children either) can relate to such goals? Most do not for a long time in their journey to learn to play.
I outline this from the beginning. We are playing an instrument to make pleasant sounds, why would anyone not listen to what they are playing. I am quite amazed at how many learning pianists worry about how they look, rather than how they sound.
“Look at me play this piece”; the wording is always telling and quite an insight to what the performers focus is. As teacher, in a lesson, I am your audience, do not offend my ears.
And they don't need to, it's perfectly fine to play just because one wants to and learn to play pieces for one's own enjoyment. The idea that it's not possible to advance with one's playing skills with such a mindset is BS.
If you play for your own pleasure, more often than not, actually achieving a level of playing that is advance is not possible. Many think it is; but they are sorely mistaken.
When an advanced level classical performer is playing music, they are not concerned with anything other than doing what the composer is asking them to do; there might be some interpretive freedom in terms of phrasing, voicing and rubato. However, the point of their performance is creating a performance of music that is bigger than them or the audience listening to it.
An amateur playing for their own pleasure is trying to recreate the energy of a performance of the music they heard. The inflections are shallow; they may be able to mimic the actions and sounds of a professional performer they heard, but that’s just it, it is shallow mimicry. To truly create an advance level of playing, you have to do your research and look at the score without any ego or sense of self.
This research means listening and playing a collection of pieces by the composer and their contemporaries, reading letters and historical accounts, listening to other pianists and how they interpreted the music, study harmony and counterpoint and any other relevant compositional skills. All this with the aim of understanding the music you are trying to play. If at any point this sounded like too much, then you will never reach a truly advanced level; there is a reason why it is expected of graduate and post-graduate students.
Some will and others don't. And the ways of the teacher will make a big difference. Most adults end up with moments of frustration and lack of motivation no matter what kind of music they are learning. It is little help if the teacher's attitude is "I told you so, now lets play level 1 music for a year". There are better ways to get through those periods.
When I ask my students to put up a ‘simple’ study, it is not an assault on the ego, but an attempt to learn new skills without the plethora of errors, hurdles and self-inflicted mountain setup by the student. How can teach you to play cantabile (a foundation skill), if you are still struggling to read the notes, and decipher the score. It makes sense to work on your voicing in a piece that requires less from you so you can focus your efforts on making a nice sound.
It is a bit of a paradox that one does usually need a teacher to really get how to play the piano well (and I too am guilty of telling people to get one when they want to play advanced music), but one will also possibly end up with one that does not have the right kind of pedagogical understanding to really be helpful.
Maybe you will become a teacher one day and be different 
Now who is cynical; I am sorry that this has happened to you to lose faith in us. Another ‘pet-peeve’, teachers who have no place to do so. I have spent my life playing, learning and teaching; how arrogant to expect to do it as a bit of extra pocket money, and do it well. Furthermore, how dare you not reflect on your teaching approach and revise your methods accordingly; again I am sorry that you have experienced this.