The term “good enough” is often misunderstood and maligned. What does “good enough” mean to you? You should expect to do work to a level “good enough” to achieve the goal you desire. If your goal is to pass this class, then “good enough” is simply achieving something above a “D.” Suffice it to say (I know this is harsh) that I do not know anyone working professionally today who will wish to hire someone with a goal to achieve anything less than “A's” and “B's.” Another reality of the professional world is that those that achieve A's are likely to receive a higher rate of compensation at the start for doing much the same work. Therefore, if your goal is to earn those A's and B's, then “good enough” takes on new meaning.
With all that said, it's unlikely that theatrical employers are going to ask about your grades, or to see your transcript. (Those wishing to work in acadamia are a different story. Plan on supplying official copies ofyour transcripts.) What your supervisors are going to watch for is a good work ethic and commitment to jobs well done.