The objectives of the study were: (1) To compare the aggression and the Self -concept among the adolescent Boys and Girls. (2) To compare the Level  of aggression and the Academic Achievement among the adolescent Boys and Girls. (3) To compare the Level  of aggression and the performance in co-curricular activities in the adolescent Boys and Girls. (4) To compare the Scholastic Achievement and Self - concept among adolescent Boys and Girls. (5) To compare the Scholastic Achievement and performance in co-curricular activities among adolescent Boys and Girls. (6) To compare the high aggression and Scholastic Achievement among adolescent Boys and Girls. (7) To compare the low Aggression and Scholastic Achievement among adolescent Boys and Girls. (8) To compare the high Aggression and Self -concept among the adolescent Boys and Girls. (9) To compare the low Aggression and Self -concept among adolescent Boys and Girls. (10) To compare the high Aggression and performance in co-curricular activities among adolescent Boys and Girls. (9) To compare the low Aggression and performance in co-curricular activities among adolescent Boys and Girls.

The sample consisted of 400 adolescent students in which 200 adolescents’ Girls and 200 adolescent Boys were taken from 23 school of district Delhi.

The following tools were used in the study: (i) Aggression Scale developed by Kumari Roma Pal and Tasneem Najvi; (ii) Scholastic Achievement from the scores of CBSE Board Examination at secondary Level ; (iii) Self - Concept Questionnaire developed by R. K. Saraswat; and (iv) Co-curricular Activities Participation Inventory developed by investigator.

Normative survey method has been used for conducting this study.

The findings of the study were: (1) There is significant different between Aggression and Self - concept in adolescent Boys and Girls. (2) There is no significant different between the Aggression and the Academic Achievement among the adolescent Boys and Girls. (3) There is no significant different believe the score of Aggression and performance in co-curricular activities. (4) There is no significant difference between the scores of Scholastics Achievement and Self - concept of adolescent Boys and Girls value. (5) There is no significant different between the scores of Scholastic Achievement and the performance in co-curricular activities. (6) There is no significant difference between the scores of high Aggression and Scholastic Achievement of the adolescent Boys and Girl. (7) There is no significant different between the scores of few Aggression and Scholastic Achievement. (8) There is no significant difference between the scores of high Aggression and Self -concept among the adolescent Boys and Girls. (9) There is no significant difference between the scores of few Aggressions and Self -concept of adolescent Boys and Girls. (10) There is no significant difference between the scores of high Aggression and performance of adolescent Boys and Girls. (11) There is no significant difference between scores of low Aggression and performance in co-curricular activities of adolescent Boys and Girls.