Why don't we study all of the people who have definitely risen from the ranks of the poor to a higher class and see what they have in common?
Sure, it's not the norm. But it happens all the time. There is enough data to form an opinion.
I'm guessing the way people rise from the poverty is much the same as people who are average becoming wealthy. They are willing to take risks (i.e., leave your neighborhood, buck the trends in your family tree) and they work on being prepared and available for opportunities that may present themselves.
We also know there are certain behaviors that absolutely correlate to and probably perpetuate generational poverty (children out of wedlock, crime, quitting school). The people I know who have risen out of inner city poverty in the U.S. (not the same as Bangladesh I know) distanced themselves from these behaviors and from the people who considered them okay.