YOU SAID:
i am going to fail this class
INTO JAPANESE
私はこの授業に失敗するだろう
BACK INTO ENGLISH
i will fail this class
INTO JAPANESE
この授業は失敗するだろう
BACK INTO ENGLISH
this class will fail
INTO JAPANESE
このクラスは失敗します
BACK INTO ENGLISH
this class will fail
That didn't even make that much sense in English.