An assessment of the Philadelphia (Pennsylvania) City-Wide Testing Program is presented to determine the effects of using customized achievement tests to achieve multiple purposes. The tests are derived from, or related to, the tests in a nationally standardized test battery, but include items written specifically to measure the local curriculum. It is generally believed that item response theory can resolve the problems resulting from this test construction process. The reading and mathematics tests developed for Philadelphia contain items calibrated on the reading and mathematics scales of the Comprehensive Tests of Basic Skills (CTBS), Form U. Data for grades 4 and 6 for 1984-86 on the reading comprehension test were chosen for the study. Results of the analysis indicate that some fairly small effects of the local curricula were found. Thus, the effect of calibrating the Philadelphia items and adding them to the CTBS set accomplished its intended purpose--to increase reliability without any serious consequences for validity. Five data tables conclude the document. (TJH)