Here is my opinion:
I believe that a teacher, even a starting one, with a reasonable amount of experience with the piano will know roughly what is within the reach of a pupil, so I would give your teacher the benefit of the doubt. On the other hand, your teacher should respect your wish. So, a compromise should be found. Your teacher already knows that you really want to play this piece. You could ask for other pieces that build up the technique required to play the target piece. That might be exactly what your teacher is doing, which would be very commendable, because IMO it's the right approach.
At the same time, I think, there is nothing wrong with you already working on sections of your target piece that are already within your reach and even those that are slightly outside your reach. If your teacher is concerned about you acquiring bad habits from bad movements, then he should show you right away what he considers to be good movements. Any reasonable student should then see right away whether a piece is doable or not and should be able to devise a proper path to it.
Have fun!