Success in the Middle Act of 201 9 This bill creates a grant program to support middle schools' efforts to identify and implement best practices for improving student outcomes and increasing high school graduation rates. Specifically, the bill directs the Department of Education (ED) to (1) allot grants to states, based on their proportion of poor children aged 5 to 17, to implement state middle grades needs analyses and, on the basis of such analyses, improvement plans that describe what students must master to complete successfully the middle grades and succeed in academically rigorous secondary school coursework; and (2) award competitive subgrants to local educational agencies and institutions of higher education, educational service agencies, or educational nonprofit organizations to implement a comprehensive middle school improvement plan for each eligible school. Eligible schools are those where (1) a high proportion of middle grade students matriculate to secondary schools with graduation rates below 67%; (2) more than 25% of the students who finish grade six, or the school's earliest middle grade level, exhibit key risk factors for failure; and (3) a majority of middle grade students are not rated proficient on required state assessments in mathematics, reading, or language arts. Funding is provided to ED to, among other things (1) contract for studies that identify promising practices for, and review existing research to identify factors that might lead to, the improvement of middle grades education; and (2) create a national clearinghouse in best middle grade educational practices.