Yuffie is an optional character so theres nothing really change the story, the only not so bad side of not getting yuffie is you wont get the Leviathan Materia.
i think you can try it again
You should be able to talk to your teacher and take it after the rest of the class took the test. Usually, if you do not take your final, you fail the class. Hopefully that isn't the case for this.
Getting a zero on your final can drop your grade by at least two letters, so there is a good chance you would fail.
fail
You fail!
NO
Then you fail
They would all fail, they work together.
You fail
you will fail the grade that you are in
you fail
You fail at English