This publication reports the results of a research study on the feasibility and validity of various accommodations in the context of mathematics assessment. The study compared limited English proficiency (LEP) and non-LEP students' scores on 20 science items under three different conditions: standard National Assessment for Educational Progress (NAEP) condition (no accommodation), customized dictionary, and glossary. The analyses provided clear results with respect to the performance levels of LEP/non-LEP students, the effectiveness of the accommodations for LEP students, and the validity of the accommodated assessment. It was found that some accommodations would actually benefit all students, while others are useful in removing barriers to participation of special-needs students. Appended are: (1) Follow-up Questionnaires for three groups: Control, Dictionary, Glossary; (2) Science Background Questionnaire; (3) Demographic Form; (4) Science Teacher Questionnaire; (5) Test Administrator Script; (6) Administrator Feedback Form; (7) Letter to the Principal; and (8) Multivariate ANOVA Results for Follow-Up Questions, Dictionary Booklet. (Contains 16 tables, 2 figures, and 2 footnotes.)