My dad was ecstatic to leave high school and formal education; he worked as a milkman, a type-setter handling hot lead that left his hands rough and calloused, a farm worker between jobs, etc. He retired after 20 years as an elementary school janitor.
He’s one of the most intelligent people I have met in my life, based on the D&C definition. He’s also perhaps the most selfless, humble man I know. I think there's a direct correlation, perhaps even a causation, between humility and spiritual intelligence.