Charter Schools in Newark: The Effect on Student Test Scores, published by the Manhattan Institute, attempts to estimate the effects of charter school enrollment on student test scores. The report exploits a random component of Newark’s school enrollment system to isolate the effect of charter schools on outcomes. This method credibly creates a natural experiment that compares outcomes between students who were offered charter seats and those who were not. However, the students who apply to charter schools differ significantly from the greater Newark student population, in that they are less likely to be English language learners or have special education needs. But the report never addresses this core issue of external validity. It also fails to note that teachers in the studied charter schools are less likely to remain in their jobs more than a few years, and fails to address a critical policy question: Can these charter schools’ financial models be sustained as they expand and enroll a different student population? While this report confirms previous work showing a positive charter effect on test scores in Newark, it fails to address these and other critical issues stakeholders must understand to formulate good charter school policy in New Jersey and elsewhere.