The judgment of whether or not a city's Title I reading program is a success is dependent upon the length of time used in the evaluation. This study's findings that estimates of achievement rates and judgments of success were dramatically affected by the length of time used in the evaluation was consistent across all the compensatory education programs investigated. Specifically, the inclusion of the summer months in an evaluation often reduces considerably estimates of achievement and hence monthly achievement rates. In other words, achievement gains made during the school year were not sustained even until the next fall. These findings are based on analysis of matched, longitudinal samples containing over 8,700 students and are unaffected by grade level, the subject area, the program, the standardized achievement test or the metric used in the analysis. (RC)