The more help students get, the better. It is therefore reasonable to ask students who took the class to help students who are currently taking this class. This arrangement also help the helpers: it is known that the best way to learn the material is to teach it. An important question is: how to pair the students to get the maximal effect? In this paper, we show that, under reasonable conditions, the best effect is when we match the best performing "older" student with the worst performing "younger" one, the second best with the second worst, etc.