Black millennials thought college would help them get ahead. Instead, it is setting them back. The median net worth of households with Black college graduates in their 30s has plunged over the past three decades to less than one-tenth the net worth of their white counterparts, according to a Wall Street Journal analysis of Federal Reserve data. The drop is driven by skyrocketing student debt and sluggish income growth, which combine to make it difficult to build savings or buy a home. Now, the generation that hoped to close the racial wealth gap is finding it is only growing wider.