Reference & Education, Science High school 90 average is equal to what GPA? دسامبر 18, 2024 ارسال شده توسط evek6061474 18 دسامبر The GPA would be 90.7. The letter grade assigned to that GPA would be dependent on the specific high school, Full File, and how they weigh their grades. For some schools it would equate to an A, while others an A-.