Most teachers in public schools (67.3%) will have at least one multilingual learner in their class, yet many have no preparation for supporting these students (NCES, 2022; Johnson & Wells, 2017). Recognizing this gap, school district administrators have called for more professional learning about instructional strategies for students who are learning English and academic content simultaneously (U.S. Government Accountability Office, 2009). A promising approach is professional learning that provides opportunities for meaningful collaboration between grade-level classroom teachers and ESL (English as a Second Language) teachers. Yet while ESL teachers are often better prepared to support multilingual students' oral language development, grade-level teachers are often better prepared to promote reading and writing. Creating opportunities for co-planning and aligning instruction can bridge that gap, but research on such collaborative learning efforts has been limited. The BELLA (Bridging English Language Learning and Academics) professional learning program (bellapd. org) addresses this need. BELLA, which was developed and tested with support from the Institute of Education Sciences (Babinski et al., 2018; 2024a; 2024b) in collaboration with teachers and administrators, aims to enhance teachers' practices and accelerate multilingual learners' language and literacy growth by bringing together ESL and grade-level teachers in a yearlong, job-embedded professional learning experience. Multiple rigorous randomized controlled trials show that the program is accomplishing those goals and leading to increased student learning.