What should the teacher's teacher call?

Teachers' teachers are usually called "Grandpa" or "Master".

In the traditional culture of China, such a title reflects the respect and admiration for the predecessors or teachers. In the education system, if a teacher faces the teacher directly, he can use honorifics such as "professor", "doctor" and "Mr/Ms", depending on the position, education or social status of the other person. On formal occasions, you can also use "teacher" as your respectful name.