  Across the United States, a growing number of school districts are turning to
matching algorithms to assign students to public schools. The designers of
these algorithms aimed to promote values such as transparency, equity, and
community in the process. However, school districts have encountered practical
challenges in their deployment. In fact, San Francisco Unified School District
voted to stop using and completely redesign their student assignment algorithm
because it was not promoting educational equity in practice. We analyze this
system using a Value Sensitive Design approach and find that one reason values
are not met in practice is that the system relies on modeling assumptions about
families' priorities, constraints, and goals that clash with the real world.
These assumptions overlook the complex barriers to ideal participation that
many families face, particularly because of socioeconomic inequalities. We
argue that direct, ongoing engagement with stakeholders is central to aligning
algorithmic values with real world conditions. In doing so we must broaden how
we evaluate algorithms while recognizing the limitations of purely algorithmic
solutions in addressing complex socio-political problems.
