It's rude to leave class before it's finished.
Kenny is in his last class of the day when he starts to feel a bit nauseous and feverish.
Kenny wants to feel better.
Kenny sips some water and sticks it out until the end of the class to avoid causing a disruption.
Kenny quietly gets up and leaves class to visit the bathroom.
Kenny's professor finishes the rest of the lecture smoothly.
Kenny's professor sees him leave, loses his concentration, and is flustered for the rest of the lecture.