！
I'm gonna fail!
Literal
Fail-[regret-ちゃう].
~ちゃう is the contracted form of ~てしまう — full verb form would be 落第してしまう. Here it carries the 'oh no, I'm gonna [end up]…' nuance of regret/dismay. Exclamation mark marks alarm. Very colloquial spoken Japanese; you'd hear this from a panicked student.