Hi NitsOwl,
Congrats on getting an interview call from a top b-school!
It could be tough to explain why you're seeking to start b-school soon after switching jobs. Then again, there's never a good time to leave a job! You could always frame it as, "Getting an MBA has always been my dream. Although I would certainly like to stay at my job longer, I believe the knowledge and skills that I can gain at business school would help me become a more valuable employee should I return to my current firm, or join another company."
I think if you focus on your long-term career goals and the reasons why business school makes sense for your career, you can redirect the interviewer's attention in a more positive way.
Wishing you the best of luck in your interview!
Sincerely,
Debbie