Recommended answer:
You should not talk negatively about your current employer; and do not tell that you want a new job because you need more money.
Here is a good possible answer to the above question:
I am looking for new challenges in a prestigious school. During my discussions with one of my colleagues I got the impression that you are trying to create new programs and courses and you promote modern methods of teaching based on modern software. I got the impression that your school is very dynamic and open to innovations, especially in the field of ESL teaching.
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