The student must be rect but the teacher must persevere. The rectitude is the Golden rule: "Do to others as you would have them do to you", Matthew 7:12; the  perseverance instead is the daily determination to do good avoiding evil, its main characteristics are the resistance and the absence of fear of death. Rectitude is the path to spiritual ilumination, perseverance instead perfects ilumination. The teacher iluminate by the grace of wisdom, the student must be enlightened.
Only enlightened people, those who have received the "holy spirit" according to the Christian religion, gnosis according to philosophy, can persevere, so when we speak of perseverance we speak not of "faith" but of security in God. Is for this that Jesus affirms: "but every one that is perfect shall be as his master", Luke 6:40. Then Jesus will promise to his disciples the holy spirit in Pentecost, Fact of the Apostle 2.
The Spiritual Gifts are defined as perfections, excellencies. We observed perfection in the creation  and we attribute to God their source.
The Spiritual Gifts define the culture of the excellence, be perfect as God is perfect (Matthew 5:48). In this scheme the virtue and justice in particular, are forms of error. The Virtue defines us a mediocrity without risks.
Practice the virtue is to practice the error. That is why grace is so necessary, the suffering is the result of practicing the error. Search for perfection is to seek the gifts of God. Live the spiritual gifts is to search the correct and the best.
We can not exceed God's Wisdom and Retitude and that means the text when it says "the student is not superior to the teacher", but instead we can achieve the superior gifts by grace, or to say we can achieve by the divine goodness the perfections of the likeness (love for the good), the emulation (gift of counsel) and image (fruits of the spirit) and so when we are "perfect" be like God, the true teacher, the perfect master.