> This is culturally alien to me; the students receiving the benefit are not harming other students. I don't think that this is culture. I believe that this is

> This is culturally alien to me; the students receiving the benefit are not harming other students. I don't think that this is culture. I believe that this is just math. If we devise some system that solves some optimization problem, we shouldn't meddle with that system by other means, like "common sense". We can use common sense to find possible improvements to the system, but we shouldn't apply this improvements without checking them with science laying behind system. Unchecked common sense can break system's promises entirely. > Solution: only allow trades that are in accord with the students' submitted preferences. That is, if Alice prefers Central to Devonshire, and Bob prefers Devonshire to Central, then we could allow Alice and Bob to switch if their submitted rankings indicated that these moves were consistent with their desires. There would be no incentive to lie. How could we know their desires? If Alice and Bob start to think creatively about it and find a way to lie about desires? Maybe they find some tradeoffs, like less chance to get into their top school against more chance to be able to trade then? The more complex system is, the more loopholes in it, the more complex and obscure strategies becomes available.