At the request of the Oklahoma Department of Education, the Technical Assistance Center 3 West conducted a statewide review of local Chapter 1 evaluation data to provide possible explanations for the unusual standardized test score gains or losses reported by a number of local school districts. During the two months of quality control visits, 35 districts were interviewed. A checklist, which is appended, was designed to record the different types of quality control errors that were found in each district. The six most frequently occurring errors are described: (1) use of outdated tests; (2) students tested outside norm dates; (3) students tested at non-equivalent periods of time; (4) incorrect norm tables used; (5) greater than 25% rate of chance-level scores; and (6) use of improper out-of-level testing procedures. The implications of and suggestions for overcoming the detected errors are presented. As a result of this study, policy changes were implemented at the State Education Agency level which altered testing practices, data collection, and aggregation procedures throughout the state. (PN)