Olympiad exams, whether national or international, can only be attempted by students enrolled in Classes 1 to 12. Thus, only pre-university students can participate in these exams. So, if you have completed your 12th standard or equivalent exam, you will not be able to appear for the Olympiad exams. Students should thus use the opportunity to attempt these exams when they are in school as they will not be able to participate in any Olympiads once they pass out from school.