Many children speak language varieties (dialects), such as African American English (AAE) that differ from the language variety typically used in academic settings and in literacy instruction (Mainstream American English, MAE). There has been considerable work suggesting a negative correlation between use of a non-mainstream dialect and lower literacy scores, suggesting that early instruction on dialect differences might be helpful for non-mainstream dialect speakers. We tested this for a population of AAE-speaking children in kindergarten and first grade. Schools were randomly assigned to teach a curriculum that explicitly compares MAE and AAE or to a business-as-usual control. While students in both the intervention and control conditions showed increased usage of MAE and greater decoding skills over time, there was no condition effect for decoding skills and minimal evidence of a condition effect for recognition of different dialects. We discuss potential limitations of the curriculum and other considerations for supporting AAE-speaking children as they start school.