<p>It’s not great, obviously. But I would only say that it’s a real problem if 1) it’s in a core MIT subject, and 2) there aren’t other indicators that it was a fluke and that you do have the ability to succeed in that subject.</p>
<p>For instance, if you got mostly As in your math classes, including your AP Calc class, and an 800 on your SAT II Math IIC test, but you got a 1 on your actual AP Calc test, it would be reasonable to infer that you had a really poor calculus teacher (since you apparently were performing great in his/her class despite not understanding the subject at all), or that you were sick on the day of the test, or just had a really bad day, or something similar, and it probably wouldn’t hurt you. Because the other evidence provided indicates that you do have mathematical ability.</p>