Despite recently reported positive associations between active-learning instruction and STEM performance and persistence, the impact of active learning on the success of HSI two-year college, and 4-year college transfer students remains largely unstudied. Responding to the need for research on effects of particular strategies, this project will deploy and assess an instructional method/curricular focus concurrent with mentorship that is novel for the target population, and rich in the practices deemed essential for its success (e.g., frequent faculty interactions, and content-based peer-collaborations). Thus, this project will contribute to filling knowledge gaps on successful STEM interventions, and identify factors bearing upon the success of the target population. Addressing the need to build capacity to improve STEM teaching at two-year HSIs, this project will forge faculty collaborations across two- and four-year institutions, seeking to improve performance and persistence of the target population before and after transfer. The project goals are to design, implement, and assess interactive-engaged (IE) problem-solving courses complemented by mentorship for pre-calculus students at a large two-year HSI, and pre-calculus/calculus transfer students at a four-year emerging HSI. Curricula will be co-developed and IE-training will be collaborative. Outcomes will be assessed using locally relevant (e.g., final exams) and validated, national-scope measures (e.g., concept inventories), enabling comparison of target-group performance gains with national ones, and consistency of performance measures across time and institutions. Qualitative analyses of essay survey data will identify emergent themes in target-group perceptions of mentorship and overall project impact.