THE ACHIEVEMENT OF STUDENTS IN DAY SECTIONS OF SIX JUNIOR COLLEGE COURSES WAS COMPARED WITH THAT OF STUDENTS IN PARALLEL EVENING SECTIONS OF THE SAME COURSES. IN A SECOND PHASE OF THE STUDY, THE ACHIEVEMENT OF STUDENTS UNDER 21 YEARS OF AGE WAS COMPARED WITH THAT OF STUDENTS AT LEAST 21 YEARS OLD. ACHIEVEMENT GAINS WERE MEASURED BY COMPARISON OF RESULTS OF A PRETEST WITH EVALUATIONS MADE AT 6-WEEK INTERVALS. IN GENERAL, EVENING STUDENTS PERFORMED AT LEAST AS WELL AS THEIR DAY CLASS COUNTERPARTS, REGARDLESS OF WHETHER ACHIEVEMENT WAS MEASURED BY TEACHER-CONSTRUCTED OR STANDARDIZED TESTS. YOUNG LOW-ABILITY STUDENTS IN THE EVENING CLASSES PERFORMED BETTER THAN CORRESPONDING STUDENTS IN THE DAY CLASSES. THIS DISSERTATION IS AVAILABLE AS DOCUMENT NO. 65-9419 FOR $3.00 ON MICROFILM OR $4.80 IN XEROGRAPHIC COPY FROM UNIVERSITY MICROFILMS, INC., 313 NORTH FIRST STREET, ANN ARBOR, MICHIGAN 48107. (AD)