Within aptitude areas (Mechanical, Administrative, General, or Electronic) in the Air Force, some technical schools require higher levels of aptitude for admission than do others (for example, there are G10 schools, G60 schools, and G80 schools based on General test scores in th 10th, 60th, and 80th percentiles respectively). The schools, however, give grades on a scale from 70 to 100, regardless of the difficulty of the school curriculum. This means that a score of 82 in a G40 school is recorded the same as an 82 in a G80 school although the scores in a G80 school must indicate a higher level of performance than the same score does in the G10 school. This study is an evaluation of a method of adjusting technical school grades issued by schools of varying difficulty so that a new criterion is formed with all school grades adjusted to the same metric. This new criterion was then used to recompute aptitude indexes, which were compared with aptitude indexes computed in the conventional manner. The new aptitude indexes predicted school grades in a cross-validation sample better than did conventional aptitude indexes. (Author/BW)