In a context where linguistic diversity in the classroom is natural, educational assessment       raises new challenges that demand the conjunction of different perspectives. The equity in the assessment process requires considering facets related to the psychometric properties of the tests, the development of linguistic competence, or the sociolinguistic context throughthe incorporation of context variables into the predictive models of performance. By analyzing population data from compulsory secondary education schools which offer more than one linguistic educational model in the Autonomous Community of the Basque Country (N = 45), this paper examines the responses of 2783 students to a mathematical competence test. The methodological approach is twofold; it includes a psychometric study of equivalence through the estimation of the differential item functioning with regard to the family language and the linguistic educational model, and the estimation of mixed linear models for the prediction of the mathematics competence. The results show: a) the equivalence of the assessment test in relation to the family language and educational model, b) the significant impact of the linguistic context variables on the competence estimation, c) the lack of significance of the linguistic models on performance. It is concluded the importance of conducting studies of differential functioning, and the incorporation of linguistic variables in the prediction of mathematical competence