Three studies of English-speaking, Spanish-speaking, and English/Spanish bilingual children, including a study of language background differences in the relationships between scores on the Teacher Rating of Oral Language and Literacy (TROLL) measure and the Preschool Language Scale-4 (PLS-4), a comparison of the TROLL scores of the children of the three groups, and a study of the language backgrounds of children scoring below the 10th percentile, based on data from 353 children in early childhood education programs in an urban area of the Southwestern United States