The Peer Enabled Restructured Classroom (PERC) program is a peer-teaching model developed by the Math and Science Partnership in New York City (MSPinNYC) to help underachieving and historically at-risk urban students succeed in math and science courses. Although preliminary success of this program has been substantial, there has not been a consistent investigation of the model's impact with participating ELL/F-ELLs. The focus of this study was to examine the effectiveness of the model with ELL/F-ELLs in a five-week summer program. Although peer-instructors received a three-day orientation and daily seminars, they were not specifically trained in ELL/F-ELL strategies. Questions investigated in this study were: Do bilingual TAS make use of the approaches, behaviors, and strategies that are consistent with the research on second language and content learning? Does the use of the native language by the bilingual TAS, those with linguistic abilities to clarify information, to answer questions and to promote higher level thinking in the primary language, help ELL/F-ELL students to process challenging content area curriculum and achieve academic success? Data based on test results, surveys, interviews, and observations were analyzed. Results indicate success with ELL/F-ELL students but with much underutilized potential. (Contains 7 tables, 1 footnote and 1 figure.)