I think the word "teacher" is too casual. So, can I say a "mentor" instead of "teacher"?
Native speaker’s answer
Rebecca
The use of the term "mentor" depends on the student, of course! However, since we can see that Anne Sullivan's care for Helen Keller extended beyond just teaching and concerned her personal life and well-being as well, "mentor-mentee" can also be used to describe their relationship. Ex: I consider my mother to my mentor. Ex: It was through the help of my mentor that I am so successful today.