YOU SAID:
I am tired of classes
INTO JAPANESE
私は授業にうんざりしています
BACK INTO ENGLISH
I am tired of the class
INTO JAPANESE
私はそのクラスにうんざりしている
BACK INTO ENGLISH
I am tired of that class
INTO JAPANESE
そのクラスにはうんざりしています
BACK INTO ENGLISH
I am tired of that class
You've done this before, haven't you.