The effects of two components of formative evaluation (frequency of measurement and data utilization) were compared to isolate formative evaluation components which teachers might routinely use to monitor achievement in learning disabled students. Fifty-two learning disabled and educable mentally retarded elementary students enrolled in regular class programs and receiving reading instruction in a special education resource room were randomly assigned to either a pretest non-data-based change group, a daily measurement non-data-based change group, a daily measurement data-based group, or an untreated control group. Analysis of results of oral reading data supported daily measurement and data-based changes as effective components of formative evaluation. (Author)