Why did slave owners prevent slaves from being educated?

Slave owners didn't want their slaves to be educated.

It was better for their slaves to not be educated so they could:

(let's use farming as an example)

1. spend more time doing work on the farm

2. Wouldn't aspire to do more in life than work on the farm.

3. Wouldn't ever question or speak about against the slave owner.

4. Not be exposed to the outside world as much as possible.