This project is aimed at generating new knowledge and improving our understanding of how Modified for Language Support-Worked Example Pairs (MLS-WEPs) contribute to effective mathematics learning and teaching in an ESOL (English to Speakers of Other Languages) context. The current study investigated a novel instructional approach to help English Language Learners (ELLs) develop better understanding in mathematical reasoning, problem solving, and literacy skills (listening, reading, writing, and speaking) while they are still developing their English language proficiency. The current study followed a wait-list control design, with both the treatment and control groups receiving intervention materials. The intervention materials were administered multiple times with different topics (units) throughout the study. The lessons were audio-recorded when the selected topics were taught. Pretest and posttest were given each time when the selected topics were taught. The data analysis for this study included both qualitative and quantitative analyses. The present study revealed the following results: (1) MLS-WEPs not only enhanced ELLs' ability to solve mathematical problems, but also improved their written explanation skills and enabled them to transfer such skills to different mathematical concepts; (2) when controlling ELLs' prior knowledge, the effectiveness of the MLS-WEPs intervention did not vary by their English language proficiency; (3) the MLS-WEPs intervention materials facilitated teachers to provide ELLs with more opportunities to read, write, and speak in mathematics and enabled teachers to ask more and deeper questions. However, worked example comparisons did not appear to motivate the participant teachers to promote equitable participation in mathematics classrooms. These findings provide direct empirical support for the need to reform mathematics teaching and learning in the ESOL context. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]