A teacher's patience with his students is based on his attitude toward them.
Rabbi Yaakov Neiman related that when he was a student in Europe before World War Two, he entered the home of his teacher Rabbi Moshe Rosenstein and observed that his teacher was testing a young child on what he had learned that week.
Rabbi Neiman asked him who the child was, and Rabbi Rosenstein whispered, "He's a child of the Almighty."
Noticing the puzzled look, Rabbi Rosenstein explained. "If I told you he is the son of this or that person, you would then feel that you know his identity. But the identity that an educator has to keep in mind is that all of his students are children of the Almighty."
When a teacher has this attitude, he will have the patience to educate each student at his own unique pace.
(Darkai Moshe, p.167; Rabbi Pliskin's Gateway to Happiness, p.207)