This article presents the secondary validation of the Brief Acculturation Rating Scale for Mexican Americans-II (Brief ARSMA-II) for use with children--carried out using two samples of Mexican-descent children (ages = 9-11) from two states ( N = 295). The Brief ARSMA-II was originally normed on adolescents and adults but has been validated and used with children. Ethnic identity development perspectives suggest that the interpretation of scores derived from acculturation measures normed on adolescents and adults may not extend accurately to children. Convergent validity and differential discrimination between groups were examined using scores on the Brief ARSMA-II; scores on an acculturation measure designed for the present study, the Things About Me (TAM); and traditional proxy measures of acculturation. Results from this study do not support the use of the Brief ARSMA-II with children. The importance of considering contextual effects in the interpretation of scores of children's acculturation experience is discussed. (Contains 2 tables.)