The purpose of this mixed methods study was to investigate relationships between students' ALEKS usage, teachers' implementation of ALEKS, and student performance on the 2017-2018 LEAP 2025 mathematics assessment. The quantitative portion of the study involved district-level analyses and teacher-level analyses that explored relationships between students' ALEKS usage and LEAP performance. The qualitative portion of the study took into consideration previous research findings that have reported associations between program implementation and student achievement. This portion of the study included thematic analyses that examined the following relationships: ALEKS implementation in relation to teacher groups (i.e., RtI 8, Math 8, Both, and Magnet), ALEKS implementation of each teacher and LEAP performance, and ALEKS implementation in relation to teacher rankings (i.e., high student achievement or HSA/low student achievement or LSA) and LEAP performance. Key findings from the quantitative analyses indicated that ALEKS usage in terms of time spent and concept mastery did not make a statistically significant impact on students' LEAP performance for any of the teachers except one teacher. In contrast, ALEKS usage in terms of skill mastery made a statistically significant impact on students' LEAP performance for HSA teachers and for one LSA teacher. However, low usage of ALEKS in terms of time spent limited my ability to fully assess the potential impact of ALEKS usage on students' LEAP performance. Key findings from the qualitative analyses indicated that there were differences in ALEKS implementation amongst teacher groups. To control for group differences, this study focused on Math 8 teachers who used the ALEKS Middle School Math Course 3 curriculum; these teachers were ranked into student achievement groups HSA and LSA. In essence, ALEKS implementation of HSA teachers were more closely aligned with ALEKS (2017) Best Practices for program implementation compared to LSA teachers. ALEKS implementation of LSA teachers typically deviated from ALEKS (2017) Best Practices. Overall, these findings suggest that despite low usage of ALEKS in terms of time spent, teachers who more closely followed the recommendations of ALEKS (2017) Best Practices had positive statistically significant associations between students' skill mastery on ALEKS and LEAP performance. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]