The central purpose of the present study is to assess the early numeracy skills of Chilean kindergarten students, taking into consideration the socioeconomic status (SES) of the schools they attend. A sample of 19 urban schools and 498 students were used for the study. "Research Findings": The data analysis showed statistical differences in the results of students from low SES schools compared with medium and high SES schools in four symbolic number tasks: counting fluency, oral number identification, oral number comparison, and non-oral number comparison. Hierarchical regression analyses revealed a direct contribution of school vulnerability index, non-symbolic number tasks, and symbolic number tasks in number comparison performance. These analyses also revealed that school vulnerability index made a loose predictive contribution when symbolic number tasks were introduced into the model. "Practice or Policy": The achievement gap detected in the early stages of formal education will most likely increase with time. Early detection of mathematics learning difficulties, effective intervention, and training of teaching staff may be means of equalizing the performance of students from different socioeconomic backgrounds.