There is a well-recognized national need for more K-12 students to pursue undergraduate education and careers in STEM, especially students from underrepresented backgrounds. The overall goal of the High-school Research Initiative (HRI) is to broaden and diversify the national STEM workforce by integrating scientific research experiences into the high school science curriculum in a way that supports students' matriculation into college and their persistence in science. HRI is a partnership between under-served high schools in central Texas and two nationally recognized STEM education programs at The University of Texas at Austin (UT): the Freshman Research Initiative (FRI) and UTeach. FRI is an ambitious program that involves 800+ freshmen and sophomores in conducting scientific research through research streams. In each stream, 40 undergraduates are mentored by a PhD-level Research Educator, a faculty Principal Investigator, a graduate teaching assistant, and undergraduate peer mentors in conducting independent research projects related to the scientific theme of the stream, such as designing DNA aptamers as biological sensors, developing software apps for clinical diagnostics, and examining changes in neural circuitry during learning and memory. Prior to joining a stream, undergraduates complete a research methods course, originally developed by UTeach to engage science and math majors in the inquiry process as part of their preparation to become secondary math and science teachers. HRI will combine FRI's model for involving students in research at scale and UTeach's inquiry curriculum and instructional approach. Specifically, HRI will involve the development, implementation, and evaluation of a yearlong, dual-enrollment, inquiry/research course, titled Research Methods (RM). The Research Methods course aligns with the emphasis on science practices in the Next Generation Science Standards, and will help schools meet the new Texas high school graduation requirements. When HRI reaches full scale, 250 students and 10 teachers will work with 10 FRI research streams each year to conduct original, publishable research. Students will develop skills in the design, conduct, interpretation, communication, and ethics of science research, and teachers and scientists will develop skills in mentoring students in research. Evaluation will provide rigorous evidence of the impact of participating in HRI on important outcomes for all participants that are linked to student persistence in science, most notably students' enrollment in college and pursuit of science majors.