How do I tackle the interview question "why join here and not your former college"?

Question

Background : I did both my bachelor's and master's degree from the same institute, let's call it institute X. I liked it there during my bachelor's and since very few institutes near by offered a master's degree in the subject I wanted I joined it. It is a decision I regret. The level of the course and syllabus was very poor and most lectures couldn't give us proper guidance on the books one should refer to for self study. I did manage to find out through a very helpful professor from a highly reputed institute how to go about things and managed to get in to a good institute for a PhD. Now I am on verge of finishing and plan on applying to institute Y for teaching position.

Question : I am bound to be asked by the interview panel of institute Y why I am choosing to apply for a teaching position there and not in my own institute. What is the best way to answer?

The real answer to the question is that standards in institute X are falling and the academic environment there is deteriorated. More importance is being given to looking good on paper than to teaching. For example, they show statistics of how you have such a great number of students doing exceedingly well in exams but having written those exams myself I know that they aren't all that challenging to begin with. There are similar exaggerated facts that make the institute look good on paper. I know that I won't be happy there unless there is a radical change.

I don't think I should be saying all this to an interview panel though (or should I?). I really want to give an honest answer but I certainly don't want to come off as some one who insults their Alma Mater even if what I say is true. So what is the best way to answer? Or is there a polite way to say that I don't like the atmosphere there?

EDIT - I would like to add that I am from Bangalore, India.

Thank you.

Answer 1

If they ask, be diplomatic. Slagging off your old institution doesn't send a good message. Something like:

While I enjoyed my time there and feel they helped me to grow into an independent researcher, I'm now looking to gain experience of working in a different department in order to develop these skills further.

might work, if true (or at least true enough for a job interview).

Then expand on this by explaining why you chose to apply to this new institution, rather than elsewhere, by explaining what you see as their positives.

Answer 2

You are leaving X because they are too focused on statistics and not so much on good teaching. Instead, you are joining Y. One should thus assume that you did some research and know how Y deals with teaching. This can be used as an argument, e.g.

I think that it is important to put high priority to good, quality teaching. As I read on your homepage/as professor A from your institute told me when I met him last week/..., you seem to agree.

In this way, you don't blame your former institute, as you don't say that they have bad teaching there. Maybe they just have "regular" teaching and you are looking for the best there is, meaning institute Y?
Furthermore, I would suggest to find out about teaching policies at Y if you haven't already, you don't want to end up at an institute that is even worse than X, do you?