This training guide is designed to help monolingual English scorers accurately measure the performance of Limited English Proficient (LEP) students on large scale assessment of open-ended mathematics and science performance tests. The guide can also help teachers accurately evaluate classroom work. The guide is arranged in such a way that it can and should be adapted to local training conditions and to needs of various large-scale classroom endeavors. In responding to open-ended assessment items, LEP students are required to read, interpret, devise a solution, write out their mathematical computations, and, very often, communicate their reasoning in writing. Guidance is provided about linguistic issues in the students' native language, developmental benchmarks, associated with learning English, and cultural influences--all of which affect the written responses of LEP students. This document contains linguistic training guidelines, a brief discussion of issues related to the accurate development of assessments for this population, and a glossary of terms. (Contains 12 references.) (KFT)