Learner-centered methodology like peer review is problematic in the pluralism of the ESL classroom when teaching academic English composition. A distinct complication is the form writing instruction should take given the interaction and variations between ESL students' L1 background, experiences, schema, and the meaning of academic literacy in both the target language culture and the student writer's L1 culture. Quantitative and qualitative methods were used in this quasi-experimental study that examined that first examined the perceived L2 writing proficiency of 122 participants in terms of the academic English writing skills and abilities of generation 1.5 students, immigrants/refugee students, and international students brought to an advanced ESL composition course. Then, the study proceeded to investigate the effectiveness to peer review training, the treatment, to improve the quality of academic English writing for mixed groups of L2 writers in two classes at a local community college in Southern California. The results showed that the experiences and perceptions of academic literacy for different types of ESL students did not match ambitious standards and expectations of the ESL college-level reading-to-writing curriculum. Peer review training moved students' development of academic English literacy and voice along further than general writing instruction alone. More importantly, the results also indicated that critical thinking was a pre-requisite to the development of academic written and oral discourse, and the evidence that supported this claim came directly from L2 writers in the treatment class. However, the development of critical thinking skills for all L2 learners within an ESL program requires the collective efforts of ESL administrators and L2 teachers at all levels because peer review training would be more fruitful in an advanced ESL composition class where reading skills, grammatical competency, and oral proficiencies were more evenly matched. [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/en-US/products/dissertations/individuals.shtml.]