The impact of achievement testing on a Spring-Spring vs. a Fall-Spring basis in evaluation of compensatory education programs is examined. The effects of the summer vacation period and crossing test levels were examined. Significant decreases in achievement test scores were found, at all grade levels, between Spring and Fall test administrations. Substantially larger decreases were noted when testing levels were crossed. The implications of differences in achievement scores, a function of time and level of testing, are discussed in terms of the RMC Title I evaluation models and the current emphasis placed upon longitudinal examination of compensatory programs. (Author/RC)