Debates about exam grades and retaking tests tend to coalesce, eventually, around the same arguments. One faction prioritizes subject mastery, the idea that it’s more important to continue to move students toward knowledge than to punish them with a bad grade. The other side emphasizes personal responsibility, insisting that there are very few second chances in life, and that regular opportunities to retake tests simply teach kids that consequences are negotiable.

But in a recent Facebook and Twitter poll about whether our teachers allow makeup tests, the discussion took a more practical turn. Most teachers agreed that retesting was sometimes appropriate, but expressed concerned about setting clear limits around the practice. A widespread problem: When given the option of retests, students often gamed the system, failing the initial exam to see what it looked like—and then simply regurgitating the correct answers later. Under those circumstances, it’s a net-zero game: Neither subject mastery nor personal responsibility is achieved.