I never failed a class. Never.
I wasn't a particularly brilliant student, but on the other hand, I was very active in Student Union affairs and in student politics.
I wasn't the guy who got straight As. I got As and Bs and a couple Cs.
I was a mediocre B-average student throughout my school years.
I didn't have a very starry school career, I was medium to above average, nothing special.
I made good grades in school.
I was a good student and stuff like that.
I was not a great student.
I was always a very good student.
I have this rather amazing report which, roughly speaking, says I was the worst student the biology master had ever taught.