Considering the number of engineers, scientists, health professionals, lawyers, nonprofit workers, etc. at b-schools, having non-business work experience isn't an issue - it's about the quality of work experience ("quality" being a subjective thing of course).
However, how your teaching experience will be viewed depends on the nature of the experience. If it's a "teaching English overseas" sort of thing, it'll be seen as a working vacation and not as a real career-oriented position. In any case, what will matter is how you execute your application and what else you have in your history -- extracurriculars, etc. that will show you to be an accomplished young person since graduating from Penn.
Alex Chu
alex@mbaapply.com
www.mbaapply.com
http://mbaapply.blogspot.com