Microschools are an alternative to traditional schools for families who might be dissatisfied with local school options. Typically, "microschools" are defined as small, tuition-based schools (serving around 15 students) that are designed to offer a more personalized and flexible learning experience compared with traditional schools. Interest in microschools has grown steadily in recent years, but the impacts of microschools on student academic achievement are yet to be rigorously evaluated. Using a combination of systematic literature review and surveys and interviews with microschool leaders, the authors provide an overview of the microschooling landscape and articulate key considerations so that future impact studies can be designed to support valid and trustworthy inferences about microschool impacts. The authors specifically address (1) common microschool models, (2) who microschools serve and why families choose microschools for their children, (3) how microschools track and monitor student progress toward goals, (4) evidence about microschools' impacts on students, and (5) key challenges regarding the short-term and long-term sustainability of individual microschools and the microschool sector overall.