What has Huck learned in school, from reading, or from Tom Sawyer that he has retained and found useful?

Huck can read and write which often comes in handy. I think Huck has also learned critical thinking skills . He can see through Southern bigotry and morality. Huck is able to develop his own value system based on his own observations rather than what he has been told. Huck even sees through Tom Sawyer's overly elaborate plan to save Jim.