Past studies examining the cognitive function of bilingual school-aged children have pointed to enhancements in areas of executive control relative to age-matched monolingual children. The majority of these studies has tested children from a middle-class background and compared performance of bilinguals as a discrete group against monolinguals. The objective of the present study was to determine if cognitive enhancement from bilingualism is sensitive to the child's degree of bilingualism in a sample of eight- and nine-year old Spanish-English bilingual children of low socioeconomic status. The results showed that the more balanced the children were in their language skills, the better they performed on non-verbal tasks of cognitive function. These results support an additive view of bilingualism, where more balanced proficiency in two languages is associated with more enhanced cognitive function, regardless of socioeconomic background.