Developing Mathematical Ideas (DMI) is a professional development program designed to increase teachers' knowledge of fourth grade Common Core math fractions and rational numbers with the ultimate goal of improving fourth graders' math achievement.

A study conducted in the 2014/15 school year, prepared for the Institute of Education Sciences by Madhavi Jayanthi and colleagues at Instructional Research Group and REL Southeast, investigated the effects of DMI on teacher content knowledge and their students' subsequent achievement in fractions. A total of 264 fourth grade teachers in 84 elementary schools in Florida, Georgia, and South Carolina were randomly assigned by school to receive either DMI (n=42 schools, 129 teachers) or their usual professional development program (n=42 schools, 135 teachers). The 84 schools were matched on grade four enrollment, number of students who exceeded fourth grade math standards, percentage of African American and Hispanic students, and percent of students eligible for free- or reduced-price lunches. In fall, 2014, DMI teachers received eight 3-hour training sessions conducted over four days, followed by homework, and concluding with a test on fractions. A total of 4,204 fourth grade students' (2,091 E, 2,113 C) baseline scores on third grade standardized tests were used as a pretest, because most third graders know little about fractions, and the Test for Understanding of Fractions was used as the posttest to measure their knowledge gain after their teachers had completed DMI.