Context: Research has demonstrated the importance of teacher quality for student achievement above all other school-based factors (Aaronson et al., 2007; Goldhaber, 2002; Rivkin et al., 2005; Rockoff, 2004). Yet while states and districts have allocated significant resources toward professional learning (PL) aimed at improving instruction (Jacob & McGovern, 2015), challenges in math student achievement persist. One reason may be that the typical approaches to professional learning that are driven by district or campus priorities - rather than focusing on individual teacher needs - may fail to help teachers achieve their potential (Gates Foundation, 2014; Guskey, 2009; Kennedy, 2016; McCarthy & James, 2017; Mushayikwa & Lubben, 2009). Adult learning and motivation theories underscore the importance of allowing teachers autonomy over their own learning, as adults have "a deep psychological need to be perceived by others, and treated by others, as capable of taking responsibility for ourselves" (Knowles, 1984, p. 9). At worst, a prescriptive approach to PL may lead to resistance to the training or learning opportunities in which teachers participate (Merriam & Bierema, 2014; Knowles, 1984. Purpose: The Math Instructor Professional Learning Autonomous Network (MiPLAN) was developed to allow teachers to select, participate in, and reflect on PL opportunities of their own choice, with the goal of improving math achievement for high-need students. The PL was intended to constitute at least 80% of teachers' state-mandated PL time. This presentation will share preliminary findings from a school-level randomization study involving two cohorts spanning 2022-23 and 2023-24. These findings will provide an early look at some of the study's research questions: 1) What are the barriers to and facilitators of MiPLAN implementation? What is the impact of MiPLAN on... 2) ...teachers' attitudes and beliefs? 3) ...teachers' classroom practice? 4) ...student mathematics achievement in Grades 3-8? Program Description: The MiPLAN project is guided by the logic model shown in Exhibit 1. MiPLAN creates the conditions for teacher choice in PL by securing teachers' release from at least 80% of state mandated PL, providing resources through $8,000 voucher stipends to cover the costs of their selected PL plus additional travel stipends if needed, distributing incentives for teacher participation, and leveraging the user-friendly TEEMS platform to help teachers through the MiPLAN process. Content expertise at ESC 18-TxCEE facilitates the curation of vetted, high quality PL options, and TxCEE professional learning coaches provide support to teacher learning cycles. Teachers are encouraged to set their own learning agenda through project activities that support reflection and teacher agency. After an initial orientation, teachers select PL that meets their own learning needs with the help of a MiPLAN coach and complete at least two learning cycles over the year. Research Approach: The design is a multisite, two-cohort cluster randomized controlled trial. Schools were randomly assigned to condition within district. Half of the schools in each district were selected by lottery to participate in MiPLAN and study-related data collection activities during the 2022-23 (cohort 1) or 2023-24 (cohort 2) school year, while the remaining schools continued with their regular PL activities and only participate in study-related data collection activities. Our main impact analyses use intent-to-treat (ITT) analyses that estimate the impact of being randomly assigned to participate in MIPLAN on (a) teachers' attitudes and beliefs (RQ2, measured by survey self-report), (b) teacher classroom practice (RQ3, measured by classroom observations), and (c) student mathematics achievement (RQ4, measured by state standardized assessment scores). Findings: Recruited sample and baseline equivalence. The study sample includes 54 elementary and middle schools in 16 Texas school districts. We used rerandomization to ensure random assignment generated treatment and control groups that are similar on observable baseline characteristics (Appendix Exhibit 2). Implementation findings. Preliminary findings from Cohort 1 suggest implementation fidelity was adequate for at least half of the treatment schools (Appendix Exhibit 3). Most teachers felt they could find PL to meet their needs, and teachers largely reported that they could complete their PL and they used what they learned in their PL to improve their math instruction. In surveys and interviews, teachers reported that the support of the TxCEE coach and choosing PL aligned to teacher needs were facilitators for implementing MiPLAN. Teachers noted that a lack of coordination was a barrier to implementation, and some teachers reported having to complete MiPLAN PL in addition to school- or district-required PL as a barrier to implementation. In surveys, treatment teachers reported having more choice and being more satisfied with their level of choice in their PL. While comparison teachers attended more PL overall, treatment teachers attended slightly more math-focused PL and were more likely to "strongly agree" with positive statements about the value of the PL they attended. Impact findings. In addition to perceptions of PL choice and relevance, treatment teachers in cohort 1 had more positive attitudes than comparison teachers on constructs related to self-concept as a self-directed learner, readiness to learn, motivation to learn, and self-efficacy in math instruction. Analyses of the impact on student achievement, teachers' attitudes and beliefs, and classroom practices are underway. We will have student achievement results based on the first cohort and classroom practice and teachers' attitudes and beliefs results for both cohorts to present at the conference. Conclusions: 1. Despite the intent of the program and agreements in place before districts and schools could join, teacher choice was not as free and open as intended. 2. Nonetheless, teachers and administrators alike reported strong satisfaction with the PL that MiPLAN enabled teachers to participate in. This appears to have borne out in higher satisfaction, self-efficacy, and professional attachment when comparing MiPLAN participating teachers to teachers in the delayed implementation group. 3. Analyses will be available by the time of the conference that examine whether the teacher attitudes and beliefs correspond to positive impacts on their math instruction -- and on student math learning. 4. If the initial positive indications on outcomes are confirmed in ongoing analyses, this has implications for equitable decision making and resource allocation in school systems, even as it raises questions about sustainability.