What did Paul teach the Corinthians instead of formal education?

Paul did not give the Corinthians formal schooling; instead he taught them the preaching of the cross—Christ crucified and risen from the dead—so that by the Spirit of God they might know the things freely given to them by God.

Les explains that Paul did not put the Corinthians through grade school, high school, and college. He took these people and began to teach them the preaching of the cross; that is all Paul knew—Christ crucified and risen from the dead. The Spirit which is of God, not the spirit of the world, enables believers to know the things freely given to them, not by Paul, but by God. Human education alone cannot make a person understand the things of God unless the Spirit reveals them.

1 Corinthians 2:2

For I determined not to know any thing among you, save Jesus Christ, and him crucified.

1 Corinthians 1:23

But we preach Christ crucified, unto the Jews a stumblingblock, and unto the Greeks foolishness;

Why does Paul use himself as an example in 1 Corinthians 2, and what did he determine to know among the Corinthians?

Paul uses himself as the prime example to contrast the wisdom of this world with the wisdom of God, showing that he did not come with excellency of speech or human wisdom. Among the Corinthians he determined to know nothing except Jesus Christ and Him crucified.