Does the twelfth grade overall score of 521 for 6 years count for eligibility?

It depends. An overall score of 521 over six years for 12th grade is not a standard grading format used by most universities. Typically, eligibility is determined by your final 12th-grade percentage or GPA from a single academic year.

French universities generally require a minimum of 60% in your 12th-grade exams for undergraduate admissions. Since your score format is unconventional, you will need to have your academic records evaluated by the universities you are applying to.