I received a 65 in AP Calculus AB. I started off the year with medical issues that disabled me from attending class consistently in the beginning of the year. Despite an otherwise adequate report card, is this 65 going to destroy my chances of getting into my match/target/reach schools? I am applying as a chemistry major, have a 91 average, and perfect standardized test scores.
A 65 doesn't look great on your transcript, but it is certainly not the end of the world (particularly if there were extenuating circumstances like medical issues). Colleges understand that sometimes events beyond students' control affect school attendance and grades.
The main way to make sure that your low calculus grade doesn't have too much of a negative impact on your college applications is to explain it. One place you can do this is in your personal statement; discussing how you struggled with personal hardship and still came out of it with a 91 GPA will give colleges more information about your situation. On the Common App, there's also the "additional information" section, which asks students to briefly mention any issues that may have affected their academic record that aren't necessarily evident from the rest of the application.
Finally, having high (or in your case, perfect) standardized test scores is a great way to show that whatever issue affected you in school is no longer a factor. SAT or ACT scores show how you compare to students in the rest of the world, not just the students in your school. Read our article on how to overcome a low high school GPA for more tips and other students' success stories.