Do not pervert justice or show partiality. Do not accept a bribe, for a bribe blinds the eyes of the wise and twists the words of the righteous. Follow justice and justice alone...
I think this is harder to do than we assume.
In Deuteronomy, Moses is giving God's word regarding how the tribes and towns should govern themselves; they should appoint fair judges and officials. There is, of course, a national, governmental application of this truth. But there is also a personal, spiritual application.
We must live fairly, justly. Micah 6:8 says, "He has showed you, O man, what is good. And what does the Lord require of you? To act justly and to love mercy and to walk humbly with your God."
This means that it is displeasing to God when we make decisions based on whether we like somebody or not rather than on the facts of the matter. We are not to show preference to the people who invite us to their homes and drop off Christmas cookies. We should love them and appreciate them. But if an issue arises, we should not assume their blamelessness over someone else simply because they have been nice to us.
If two people need help, we should not automatically decide to help the one we know better and like more. We should consider the facts: who needs help the most? Who may have a support system of help other than us... and (more importantly) who may not?
This is tremendously difficult.
It is difficult for anyone in leadership: school administrators, teachers, pastors, even parents. But difficult as it may be, the Bible is clear: God is not pleased by our biases. When God is not pleased with me, I am probably in sin. Based on the Bible passage of the day, it looks as though giving in to our biases is a sin.
And speaking of "just leaders"... within each of us, our "will" is the thing that controls--leads--our decisions and actions. Our wills must be the "just leaders" of our psyches. Although many of us find it easier to follow our hearts, our memories or even our imaginations, we must surrender our wills to the perfect will of God and behave in a way that is pleasing to the Lord. We must will our behavior to reflect God's justice and fairness rather than following our natural inclinations.
Justice is a big deal to the Lord, and I think we often don't even have a clue what justice is.