Note 1 at Joh 7:15: Jesus received His wisdom and knowledge by direct revelation from the Spirit of God (see note 1 at Lu 2:26) rather than being taught by people. Jesus had been learning (Lu 2:52) but not through man. The Holy Ghost was His teacher.

All born-again believers have had this same ministry of the Holy Spirit made available to them as well. In Joh 14:26, Jesus said that the Holy Ghost "shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you." He also said the Holy Ghost would even show us things to come (Joh 16:13). The Holy Ghost has been sent to teach us this same wisdom Jesus had that made the Jews marvel, but we have to "show up for class." This wisdom has to be drawn out by faith and time spent in the Word and prayer.