The study authors examined the effects of using "Diagnostic Assessment Tools" ("DAT") on mathematics and reading outcomes for students in Indiana schools during the 2009-10 academic year. "DAT" consists of interim assessment tools--Wireless Generation's mCLASS for students in grades K-2 and CTB/ McGraw-Hill's Acuity for students in grades 3-8--modified to align with Indiana's state assessments. The intent is for teachers to use these "DAT" interim assessment results to inform their instructional practice to meet the needs of their students. The study authors found, and the What Works Clearinghouse (WWC) confirmed, that the use of Diagnostic Assessment Tools did not have a statistically significant impact on general mathematics achievement or reading achievement for the full sample of students in grades K-8. However, the authors found, and the WWC confirmed, statistically significant positive effects for grades 5 and 6 in mathematics achievement and grades 3-5 in reading achievement. The authors found, and the WWC confirmed, no statistically significant impacts on mathematics achievement in grades 3 and 4 or on reading achievement in grade 6. The research described in this report meets WWC group design standards without reservations. This study is a well-executed randomized controlled trial with low sample attrition. A subset of the analyses described in the study meet WWC group design standards without reservations. Specifically, this rating pertains to the intent-to-treat (ITT) estimates for the full (grades K-8) stayers-only student sample, which was provided in response to an author query. This rating also applies to the grade-specific ITT estimates for the stayers-only samples in grades 3-6. Appended are: (1) Study details; (2) Outcome measures for each domain; (3) Study findings for each domain; and (4) Supplemental findings by domain. [The following study is the focus of this "Single Study Review": Konstantopoulos, S., Miller, S. R., & van der Ploeg, A. (2013). The impact of Indiana's system of interim assessments on mathematics and reading achievement. "Educational Evaluation and Policy Analysis," 35(4), 481-499 (EJ1019178).]