IN 1960 AT TORONTO, CANADA, A LONGITUDINAL STUDY OF ACHIEVEMENT WAS BEGUN IN JUNIOR KINDERGARTEN WITH 8,695 CHILDREN. THE OBJECTIVES OF THE STUDY WERE (1) TO EVALUATE THE EFFECT OF JUNIOR KINDERGARTEN ATTENDANCE ON THE ACHIEVEMENT AND DEVELOPMENT OF CHILDREN, AND (2) TO EXAMINE THE NATURE OF THE WORLD OF JUNIOR AND SENIOR KINDERGARTEN CHILDREN. THE DATA COLLECTED CONSISTED OF INFORMATION AND SCORES FROM (1) THE DRAW-A-CLASSROOM TEST, (2) THE PUPIL PROFILE FOLDER, (3) THE RATING QUESTIONNAIRE, (4) THE METROPOLITAN ACHIEVEMENT TEST, AND (5) THE OTIS QUICK-SCORING MENTAL ABILITY TEST. FOUR TABLES WERE MADE TO COMPARE JUNIOR KINDERGARTEN CHILDREN WITH SENIOR KINDERGARTEN CHILDREN WHO HAD NOT ATTENDED JUNIOR KINDERGARTEN. OF THOSE WHO DID NOT GO TO JUNIOR KINDERGARTEN, MATCH 1 INCLUDES CHILDREN WHOSE PARENTS CHOSE NOT TO SEND THEM TO JUNIOR KINDERGARTEN. MATCH 2 INCLUDES CHILDREN LIVING WHERE JUNIOR KINDERGARTEN WAS NOT AVAILABLE. STATISTICALLY, MATCH 1 SHOWED JUNIOR KINDERGARTEN TO BE A GREAT ADVANTAGE. MATCH 2 SHOWED LITTLE DIFFERENCE, AND IN SOME CASES THE JUNIOR KINDERGARTEN GROUP WAS ACTUALLY SURPASSED BY THE SENIOR KINDERGARTEN GROUP. A POSSIBLE EXPLANATION FOR THE INSIGNIFICANT DIFFERENCE SHOWN IN MATCH 2 IS THAT PARENTS OF THOSE SENIOR KINDERGARTEN CHILDREN HAD JUST ENOUGH SCHOOLING TO PLACE A HIGH VALUE ON EDUCATION. THE EFFECTS OF JUNIOR KINDERGARTEN DISAPPEAR IN ABOUT 4 YEARS. IF JUNIOR KINDERGARTEN IS TO HAVE A LASTING EFFECT, THEN THE ENTIRE SCHOOL PROGRAM SHOULD BUILD ON THIS EXPERIENCE. THE APPENDIX TO THIS DOCUMENT IS PS 000 358. (CO)