The purpose of this study was to examine the fidelity of a dual immersion program implemented at a particular school site. This study sought to determine the effectiveness of the school’s dual immersion program on Spanish English learner students. This study gathered the perceptions of the students and teachers within the program and examined the impact on the program. Evaluation findings indicate that the program was not run with fidelity. Through teacher surveys and a focus group, this study found that teachers are not adhering to research-based curriculum, need more professional development, and lack a cohesive vision that reflects dual immersion program values. A review of reading data demonstrates that the students’ first language has helped them acquire their second language. This study found many implications for school sites that can be used to better serve English learners in the dual immersion program. With the guidance of the seven strands from Guiding Principles for Dual Language Education, this study determined that the fidelity of the program, student data results, and teacher and student perceptions all impacted the effectiveness of this dual immersion program. Overall, I conclude that if this program were operated with fidelity, the English learners at this school site would have more potential to achieve higher academic success.