Parents often select schools by relying on subjective assessments shared by other parents—which are increasingly becoming available on school ratings websites in the form of written reviews. We apply recent advances in natural language processing to analyze nearly half a million reviews posted by parents for over 50,000 publicly-funded US K-12 schools on a popular ratings website. We find: i) schools in urban areas and those serving affluent families are more likely to receive reviews; ii) review language correlates with standardized test scores—which are known to closely track race and family income—but not school effectiveness, measured by how much students improve in their test scores at the school over time; and iii) the linguistics of reviews reveal several racial and income-based disparities in K-12 education. These findings suggest that parents who reference school reviews may be accessing, and making decisions based on, biased perspectives that reinforce achievement gaps.