YOU SAID:

I was class president when I was in 4th grade!

INTO JAPANESE

私は4年生だったとき、私はクラス会長でした！

BACK INTO ENGLISH

When I was in fourth grade, I was the class president!

INTO JAPANESE

私が4年生だったとき、私はクラス会長でした！

BACK INTO ENGLISH

When I was in fourth grade, I was the class president!