Diverse backgrounds, viewpoints and experiences in science, technology, engineering and math (STEM) are vital for innovation and creativity in STEM; and yet, racially minoritized groups, such as African Americans and Hispanics, remain underrepresented in the STEM K-12 and career pipeline. Studies show that exposure and access to STEM experiences in the early years are especially effective for increasing interest in STEM careers and intentions to major in STEM. However, these opportunities are often unavailable and inaccessible to underrepresented racialized minority students, particularly those from majority minority schools in low income communities. We describe a model for accessible and inclusive exposure to STEM experiences, enabled by a partnership between elementary schools from low income under resourced, predominantly racialized minority K-5 schools in North St. Louis County, Missouri, and scientists at a non-profit plant science research institution, to provide STEM activities for all students over the course of a single day. The goal was to stimulate students' interest in STEM and related careers, and enrich students and teachers' STEM knowledge. Five "STEM Days" were held at four elementary schools from 2017 to 2019. Feedback from teachers and students revealed positive outcomes, including increased excitement and knowledge gains. Students showed increased STEM interest, and teachers indicated that the new approaches to classroom STEM instruction, despite the brief exposure, were beneficial. Unexpectedly, participating scientists also noted numerous benefits. We share lessons learned and suggest recommendations for practitioners in STEM.