Luke 6:40

The disciple is not above his master

(ουκ εστιν μαθητης υπερ τον διδασκαλον). Literally, a learner (or pupil) is not above the teacher. Precisely so in Matthew 10:24 where "slave" is added with "lord." But here Luke adds: "But everyone when he is perfected shall be as his master" (κατηρτισμενος δε πας εστα ως ο διδασκαλος αυτου). The state of completion, perfect passive participle, is noted in κατηρτισμενος. The word is common for mending broken things or nets (Matthew 4:21) or men (Galatians 6:1). So it is a long process to get the pupil patched up to the plane of his teacher.