The main purpose of this study is to assess effects of a previously validated fraction intervention when it is conducted classwide on the fraction knowledge of fourth-grade students with and without math learning difficulties (MLD). The study population is 4th-grade students with MLD and without MLD. Teachers agree to be randomly assigned to two conditions. In one condition, teachers include classwide fraction intervention (CFI) in their standard math program. In the other condition, teachers conduct their standard math program without CFI. CFI is implemented 2 times per week for 20 weeks for about 30 minutes each time. Students in both conditions are tested before and after CFI ends.

The study is conducted in the Metropolitan-Nashville Public Schools. Teachers decide if they want to participate. Parents of students in their classrooms decide if they want their children to participate in the study; participation means students complete the study's pretesting and posttesting, and teachers report their test scores on a school-collected measure. Students decide if they want to participate. Teachers complete a survey, report student scores on the school-collected measure, and are observed during CFI implementation.

Each CFI session comprises 3 segments. In Segment 1 (10-12 minutes), teachers conduct that day's CFI lesson. In Segment 2 (10-12 minutes), students work in pairs, taking turns being "coach" and "player" as they explain their thinking and solution strategies taught in that day's Segment 1. Students use CFI help cards to provide constructive feedback to each other. Segment 3 (5-7 minutes) is independent practice.

The primary end-points are students' posttest fraction ordering, fraction number line estimate, fraction calculations. Secondary end-points are students' performance on more distal fraction measures. Other measures are a teacher survey describing fractions instruction and reliance on CFI procedures and their perceptions of CFI's effectiveness and feasibility, as well as CFI adherence from audio recordings and live observations of teachers implementing CFI.

Inclusion Criteria:

• To enter the study, students must meet the following criteria. They must attend a Metropolitan-Nashville Public School whose principal has given permission for his/her school to participate and participate in a fourth-grade classroom whose teacher has agreed to let her/his students participate.

Exclusion Criteria:

• We exclude students with identified intellectual disability from study data collection because CFI is not designed to meet the needs of this population. There are no other exclusions.

We will make de-identified datasets electronically available to external users under a signed data-sharing agreement (see Access Criteria). The outside user submits a request describing the variables of interest and the research design. If approved, a Data Use Agreement Form will be sent to the user to complete. If approved, the relevant dataset data will be extracted and provided with relevant portions of the data dictionary. If not, written communication will be provided explaining the basis for this decision. If we are unclear, a written request for clarifications will be provided, with up to two rounds of clarifications.

Variables will become available as manuscripts reporting those variables are accepted for publication. The PI will respond within 2 months to an external user's request that describes the external user's variables of interest and research plan,

The proposed variables are part of the database; the research questions can be answered with those variables; & the research plan is internally consistent, quantitatively sound, and tenable. Also, guarantees are provided that data are used only for the research purposes described in the user's request; no individual will be identified for any purpose; the data will be secured appropriately; the data will be destroyed or returned after analyses are completed; a written research report will be provided to the PI (or her designee) within 12 months of receiving the database; and the user will cite the parent study in all presentations, written reports, & publications.