Brown and the word "robbery".....

[Thumpalumpacus]

You say that black dropout rates are caused by poverty, but if poverty is caused by high black dropout rates, then it is a circular argument.
For the circular system to exist, a third force must be in place, why are so many blacks poor and dropping out of school?

No, it's a vicious cycle, which is entirely different from begging the question. And when multiple variables are present in a dynamic, it sometimes happens that a pair of them become mutually reinforcing, minimizing or obviating the original impetus into the new status quo.

The idea that a complex social phenomenon could have one cause is overly simplistic and for that reason, likely not very useful. Variables in any equation interact.