Because it's what you want to become. If your questioning your decision maybe you need to become something else.
Job titles are usually only capitalized in business/professional material, rather than in common prose. Writing either "Physics Teacher" or "physics teacher" would be correct, but "Physics teacher" or "physics Teacher" would not.
yes a math teacher can teach physics
He was a physics teacher.
With a degree in California physics, one could work for research and development companies, become a high school physics teacher, and work for research labs or power plants.
who was ernest greens teacher
They had no chemistry
the physics of music is you have to concintrate and listen to your teacher and pay atention to the music
a physics teacher can make physic easy to study
Ask your teacher.
Teacher-physics.
It all depends upon what you want to do, if you like physics better go after physics if you like math better go after math, the only person that can answer that question is yourself.
Show them what its all about. Make it interesting.