Five major points of particular relevance to the development of the Tests of Important Educational Objectives (T.I.E.O.)--and to the Academic Ability Test in more limited fashion--are reviewed and developed further. The points are in reference to 1) practice effect; 2) errors of measurement; 3) ceiling effect; 4) equality of units; and 5) normal growth. Implications for the development of the T.I.E.O. include the importance of: 1) studying empirically the practice effect for each test proposed for inclusion in the battery, to determine how this effect varies with such factors as interval between test and retest, proportion of overlap between tests, test content, type of item, speededness of the test, and mental maturity of the subjects; 2) investigating the errors of measurement for each instrument to determine the overall standard error of measurement and the magnitude of the standard error of measurement in several parts of the test-score range; 3) building measuring instruments with sufficient ceiling to measure growth over time for all individuals for whom the test is appropriate--including the most capable students in this group; 4) studying item selection procedures to determine the best item difficulty distribution to measure individual growth over time; and 5) carrying out longitudinal studies to reveal the growth curves of individuals.