It's cause. What you're referring to is the cause of education deprivation. That education deprivation is the cause of the far lower likelihood of reaching higher wealth status.

A chain of things or events can - typically does - possess multiple causes along the pathing. A cause of a cause, is a legitimate, normal and required logical concept. Practically any outcome or condition you can name has a cause, which has a cause.

Alternatively you'd have to claim that there can only be one cause in an entire chain of events. An absurd notion.