This report assesses the validity, reliability, and efficiency of the Teachers' Rating Questionnaire (TRQ), a pupils' school success measure developed in connection with a 1961 longitudinal Study of Achievement. TRQ ratings on nearly 14,000 pupils, gathered in the Study of Achievement and a New Canadian Report, constituted the data source. Questionnaire performance was determined in a variety of ways: comparison of teachers' ratings and student promotions estimation of TRQ total score, section and question reliability; grade independence; and relationships between TRQ sections. In addition to a theoretical discussion of item effectiveness and correlations among items a detailed statistical analysis was undertaken of the ratings for a sample of students who had been assessed on all forms in the longitudinal study. While validity of TRQ adjustment and creative-expression sections was not directly demonstrated, a reasonable degree of correlation with other measures of academic success (standardized achievement test, I.Q., promotios) was found reflecting the overall validity of the TRQ, especially the performance section. A large part of the differences between any two sets of TRQ ratings were found due to differences in teacher interpretation and their perceptions of pupils. (Author/BJG)