Research on language-minority student outcomes has revealed sizeable and persistent achievement gaps. The reasons for these gaps are often closely linked with other factors related to underperformance, including generational status, race/ethnicity, and socioeconomic status. Using sociocultural second-language acquisition theories and community linguistic capital as a theoretical frame, this study builds upon the extant literature to examine the relationship between community linguistic isolation and language-minority 10th-grade student achievement outcomes. I find that language minority achievement gaps are three to five tenths of a standard deviation in reading and math but that the effect is attenuated by increased levels of linguistic isolation. These results appear robust to a number of specifications. Possible reasons for the attenuation are also discussed.