This study focused on the evaluation of the English as a Second Language (ESL) program provided to the English Language Learners (ELLs) in elementary and middle schools in one local school district. The study evaluated two factors: model of service provided and teacher effectiveness. The models of service provided were a push-in model and a pull-out model. Teacher effectiveness was determined using an observation tool which included best practice instructional strategies for ELLs. The study examined the impact that these two factors had on the reading achievement and language acquisition of the ELL students in grades 3, 5, and 8. Research methods included teacher observations, analysis of student reading achievement based on the state assessment, and analysis of language acquisition based on the ACCESS assessment. The results suggest that regardless of the program type (push-in or pull-out), grade level taught, curriculum used, teacher planning for and implementation of best teaching practices and strategies is the factor that has the greatest impact on student achievement. Teacher evaluations and feedback on instructional practices need to occur often in order to improve teacher effectiveness and therefore have positive impact on student achievement. [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.]