YOU SAID:

i have extremely bad grades in school

INTO JAPANESE

私は学校の成績が極端に悪い

BACK INTO ENGLISH

I have extremely poor grades in school

INTO JAPANESE

学校の成績が極端に悪い

BACK INTO ENGLISH

School performance is extremely poor

INTO JAPANESE

学校の成績は極めて悪い

BACK INTO ENGLISH

School results are extremely poor

INTO JAPANESE

学校の成績は極めて悪い。

BACK INTO ENGLISH

School results are extremely poor.

INTO JAPANESE

学校の成績は極めて悪い。

BACK INTO ENGLISH

School results are extremely poor.