<p>The "A" part is precalculus, a requirement to take the class at all.</p>
<p>At my school AP Calculus AB/BC is two parts. You have to take AP Calculus AB and BC. AB first semester, and BC second semester. Then you pick which AP exam you wish to take. My school also allows students to take AP Calculus IA first semester and AP Calculus IB second semester which prepares the student for the AB exam. Some schools let students choose which Calculus course to take. Calculus AB is PreCalculus based mixed with actual Calculus material. BC just takes things more in depth. It’s logical to take AB before BC, but BC is more challenging and some students just jump right into it.</p>
<p>Well, taking Calculus AB first, from what I’ve heard, makes Calc BC much easier for the good-at-math-but-not-a-genius student. So I guess some schools make it a prereq so that more students can take BC and do well in the class. At my school, though, everyone taking BC goes there straight from precalc since only the top math students take it anyway.</p>
<p>At our school, BC is known to just be AB at a faster pace + more concepts (which it essentially is). They’re both separate classes, and based on your performance in Pre-Calculus, your teacher will recommend you take AB or BC. Seems to be the most fair way of doing things.</p>
<p>At least from what I know, the classes vary by school, and so, their requirements vary. At my school, BC is a year long class that goes entirely through the AB and BC curricula; AB is a year long class getting ready for the AB exam.</p>
<p>At someone else I know’s school, AB is a year long class getting ready for the AB exam. Then, BC is a year long class covering just the BC curriculum (they finish by like January, then do practice tests forever).</p>
<p>Therefore, in the second situation, AB is a prerequisite; whereas, at my school, AB is not a prerequisite, and few people actually take AB, and then BC.</p>
<p>At our school there is a STEM magnet program whose Honors Pre-Calc class covers the “A” material in AP Calc AB. This course is a pre-requisite for BC.</p>
<p>Like everybody said, the “A” is primarily Precalculus subject matter. If you have a great math program at your school (and more importantly, a solid Honors Precalculus class), you can probably jump right into BC, but if your math program is on the weaker side, it might not teach you all that is necessary for Precalculus.</p>