The Louisiana Department of Education (LDOE) develops all mathematic standards and curricula in Louisiana. Once approved, these items become the officially mandated curricula that each school must teach. LDOE is also responsible for the flow down of the official curricula to each school system, plus providing the appropriate amount of training to the math teachers to effectively implement the new curricula. For example, in 2017, a statewide assessment provided information on student mathematical proficiency. Based on the poor results, and improved mandated set of standards and curricula, LDOE launched a rubric of approved research-based curricula required for low performing schools. One of the curriculum options was Eureka Math Curriculum. In response to the LDOE Curriculum mandates St. Tammany Parish Public Schools (STPPS) decided in 2020 to implement the same required LDOE curriculum to all schools in the district no matter their performance. This change in curriculum culminated in the third curriculum between 2017-2020 change for most math teachers in the district. This study focused on the experiences of selected math teachers charged with implementing the Eureka Math curriculum into the STPPS. The data collected consisted of structured questionnaires and semi-structured interviews with four fourth and fifth- grade teachers school system. Hargreaves (1998) "Changing Teachers, Changing Times" framed this study. Using Hargreaves's (1998) framework for the study, the researcher identified four obstacles teachers faced implementing a mandated curriculum. Finally, the researcher concludes with recommendations for best practices when implementing any mandated math curriculum. The researcher identified Eureka Math as the teachers' primary change element to implement curricula changes. Using Hargreaves's (1998) outline, the researcher identified four obstacles to overcome and offered three solutions towards the successful implementation of Eureka Math. The obstacles included: pacing and planning, lack of resources, need for increased support, and teacher autonomy. This study identifies three best practices for successfully implementing the challenging Eureka Math: increased support, leniency on the scope and sequence of curricula implementation, and a new requirement for focused and tailored instruction sessions for each level of math teachers. [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.]