The correct answer is specific learning disorder.
Specific learning disorder is a type of a disorder dealing with development of a child; during school ages, a child may experience learning difficulties when it comes to one (or more) of the key academic skills, such as reading, writing, or math. In the case above, Juan has learning difficulties when it comes to math, but not other subjects.
Her bias is known as "the outgroup homogeneity effect".
Outgroup homogeneity is the inclination for individuals to see ingroup individuals as more differing than outgroup individuals. The Outgroup Homogeneity Effect is the propensity to see an outgroup as homogenous, or as "all the same," while the ingroup is viewed as more heterogeneous or differed.
Foreign born population of the south actually decreased in the late 1800s