The purpose of this study was to investigate whether the Marzano Focused School Leader and Teacher Evaluation Models impacted school leader and teacher effectiveness to increase student proficiency and growth. This quantitative, non-experimental study was conducted using preexisting data in all middle schools in the School District of Palm Beach County, Florida for 2017-2018. Four research questions guided this study regarding the relationship and predictability among the variables of school leader and teacher instructional practice scores, quantity of observations reported in iObservation® and student proficiency and growth in Florida Standards Assessment (FSA) Developmental Scale Scores (DSS) in English Language Arts (ELA) and Mathematics or corresponding End-of-Course (EOC) assessment. The linear regression analyses indicated that instructional practice was a statistically significant predictor of Grade 6-8 FSA ELA and Mathematics or corresponding EOC performances. The linear regression analyses indicated that there is a relationship between student proficiency and growth as measured by the developmental scale mean scores on FSA ELA and FSA Mathematics or corresponding EOC. These findings were based on data for one school year, and thus caution must be taken when deducing these findings. [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.]