Better matches versus honest choices
Systems that allocate school places are an example of one-sided matching: people list their preferences, and an algorithm assigns them to the available places. However, these systems face a difficult trade-off. Some systems are designed to make truthful reporting the best option. In other words, pupils and parents have no reason to change their preference list to improve their chances. This is known as strategyproofness. However, these systems can sometimes leave pupils with a place at a school far down their list.
Other systems can give more pupils a place at one of their preferred schools overall. But they may also make it worthwhile to report preferences strategically: ranking schools differently from one’s genuine preferences in the hope of securing a better outcome.
Amsterdam’s secondary-school system illustrates this challenge. The city uses a lottery-based method called Random Serial Dictatorship, or RSD. It encourages truthful reporting, but some pupils have been assigned to schools much lower on their lists.