Nearly 1 out of every 5 students in California K-12 schools is an English Learner, yet our latest research in brief finds that the majority of teachers across the state are not being given the resources and support they need to effectively teach math to the hundreds of thousands of emerging bilingual students. The study, California Mathematics Teachers' Perspectives On The Quality Of Their Instructional Materials For English Learners, looks at survey data from teachers and addresses 4 key findings: (1) Elementary teachers broadly used the curriculum adopted by their district, while most secondary teachers used self-created materials on a daily basis; (2) Most teachers reported that their curricular materials were aligned with the math content standards. Yet, only half responded that their materials helped them to tailor instruction to support English learners; (3) The majority of teachers reported that their materials lack relevance for students; and (4) The majority of teachers reported that their materials do not support them to assess or provide feedback on English learners' development of math language. As California is in the midst of updating the state's math framework, this important research adds yet another voice to the many educators, advocates, researchers, and others who are urging state leaders to modernize math instruction. [This report was commissioned by the English Learners Success Forum. The survey was deployed by RAND through their American Educator Panel.]