Iruka was sometimes so engrossed in the lesson that he sometimes would bury his head in his lesson plan and call on the same student every single day for answers.
Sakura, after being called upon for a week in a row, asked her friends for help.
Kiba offered a suggestion. "How about this; the next time Iruka calls on you, you'll say: 'Sakura is absent today'. Then, he'll have to call on someone else."
Sakura thought this was a very good idea.
The next day, Iruka asked Sakura to say the hand signs required to perform a clone jutsu.
Sakura crossed her fingers, and said, "Sakura is absent today."
Iruka didn't look up. "Fine then. YOU can answer the question instead."