Tragedy struck during Jessica Tang’s third year of teaching at Gavin Middle School: A promising student perished in a South Boston house fire while trying to protect her little sister, exposing cracks in the state’s social service system. The 2008 death of Acia Johnson would turn into a defining moment in Tang’s career, revealing the painful limits of what teachers can do to help students. The tragedy also inspired Tang’s work as a union leader, galvanizing teachers, students, and parents to advocate for more social services in schools.