I can skip today as he won't know whether I'm there or not.

I can skip today because I really need to finish something or study for my English/History/Whatever test the next period.

I don't need to read the book because he will go over it in class.

I can wait to study until the night before the test.

I can understand what he does in class so I don't need to work all the problems.

There is no need to go to the class before a test day as nothing new will be covered.

There is no need to go to the class after a test as nothing new will be covered.

He's a nice guy and won't flunk me.

I don't have to work hard this time either because he won't flunk me again.