You may be able to play La Campanella by ear.... but how is that going to help you in being a music teacher?
What are your musical qualifications? How much performance experience do you have? How much teaching experience do you have?
It is very difficult to do well as a music-teacher when you are a young person. You will be competing directly with people who are twice or three times your age, who already have decades of experience in helping young musicians prepare for examinations and competitions. Typically, well-established teachers who have sizable studios of 20-30 kids or more will be the people in any geographical region who command the highest hourly rate.
Young people who lack experience often have to drive to people's homes to teach, and usually do so for a much lower hourly-rate than what the well-established teachers in the area charge.
I don't mean to discourage you. I simply wish to communicate to you how difficult freelance teaching can be for a young person. If you wish to be employable in this capacity, I would recommend that you first become proficient at playing from scores at sight (any level of difficulty-not just easy stuff), confident improvising, either freely or from written chord-changes in a variety of musical styles, as well as being adept at playing pieces from memory (I'm talking about having a repertoire of at least several dozen pieces, but preferably over 100, covering more-or-less every time period from about 1650 up to the present day). I also recommend being a composer as well
