<p>^^which makes sense, because as ucb notes, the more rigorous (and popular) AP’s require prereqs, and the typical Frosh hasn’t yet completed Alg II, for example. Conceivably, a Frosh could take AP Chem, since it only requires Alg I, or AP Bio, but it might be a struggle to keep up with the upper classmen. Plus, many high school districts require students to complete other sciences to graduate.</p>