Когда я учился в школе, на тот моме

Когда я учился в школе, на тот момент я был в 8 классе.

Результаты (английский) 1:

When I was in school, at that time I was in grade 8.

Результаты (английский) 2:

When I was in school, at that time I was in the 8th grade.

Результаты (английский) 3:

When I went to school, at that time, I was in class 8.