This normative comparative study sought to compare the reading achievement, in English and Spanish, of Latino English learners in a 50/50 two-way immersion (TWI) bilingual program to Latino English learners in a 90/10 TWI program. The scores from 55 students across four TWI programs, two 50/50 and two 90/10, were analyzed. The principal from each school was also interviewed. Quantitative data from the district’s reading Benchmark Book Test, California Standards Test/English Language Arts and Standards-based Test in Spanish were analyzed using repeated measures ANOVA, Bonferroni Post Hoc and Chi Square to compare the means between the students’ reading achievement in Spanish and English by program model. Overall the biliteracy results revealed that the main effect between programs was not significant (p = .23) nor was the within subjects effect (p = .42). However, the interaction of grade and program was significant (p = .001). English and Spanish literacy results showed the students in the 50/50 TWI program outperformed students in the 90/10 TWI program by end of fifth grade; however across program models more students reached grade level literacy in English than in Spanish. Interviews with the principals of each school revealed that when analyzing test data at the school site level, English data were analyzed more closely and more systematically due to accountability measures indicating that NCLB has had a profound effect on the biliteracy attainment of Latino English learners in two-way immersion.