As part of its DLL Pilot Study, First 5 California has released Math Skills Among Spanish-Speaking DLLs: Implications for Assessment, a new brief by the American Institutes for Research (AIR). The goal of the brief was to identify which Dual Language Learners (DLLs)—Spanish dominant, balanced bilingual, and English dominant—might benefit most from being assessed on math skills in their home language. It found that most Spanish-dominant DLLs scored higher on math as assessed in Spanish, compared to English. And even within the balanced bilingual group, a substantial number of DLLs scored higher on math as assessed in Spanish. These policy-relevant findings support expert recommendations for assessing DLLs in both English and their home language, particularly for DLLs who are dominant in their home language, to avoid the risk of underestimating their skills.