A quasi-experimental research study was conducted to investigate the performance of English learners (ELs) on mathematics assessments when using interactive whiteboard (IWB)-based instruction as compared to text-based instruction. A sample of 47 seventh-and eighth-grade EL students from ABC Middle School (name has been changed) was included in this study. The native language of the students included in this study is either Spanish or Haitian Creole. English learners that scored either level 1 (beginner), level 2 (intermediate), or level 3 (advanced) on the 2011 New York State English as a Second Language Achievement Test (NYSESLAT) were taught a mathematics unit using either IWB-based or text-based instruction. Two separate mathematics units were used in this study. The content is in alignment with the eighth-grade New York State Mathematics Learning Standards (New York State, Department of Education, 2005). A reliable and valid pre-test and post-test were created and were administered to all groups. Six instructional periods were used for instruction after the pre-test was administered. The researcher was the instructor for all groups and created lessons using either IWB-based or text-based instruction based on the approved curriculum materials of the district. All lesson plans were clearly written and were used as a guide. Each group participated in learning a unit of mathematics using both methods of instruction. After the unit of instruction was complete, all groups were administered the same post-test. A 2 x 2 x 2 (time x EL level x instructional method) repeated measures ANCOVA was used to examine the mean achievement scores among the subgroups with New York State Mathematics Assessment scores used as a covariate. The results showed that students made significant gains from pre- to post-test for both methods of instruction. When each unit was examined separately, analyses for Unit 1 indicated significant gains by method of instruction. Results for Unit 2 indicated significant gains by method of instruction for level 2 (intermediate/advanced) ELs only. The researcher suggests that interactive whiteboard-based instruction can help improve mathematics achievement for English learners across different levels of English proficiency, as compared with text-based instruction. [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.]