A student who is on the fence regarding taking an additional AP course and exam can look at the schedule of AP exam dates (I assume they are published well in advance), since students do worse on AP exams taken close together:
http://www.nber.org/papers/w18436The Impact of Time Between Cognitive Tasks on Performance: Evidence from Advanced Placement Exams
Ian Fillmore, Devin G. Pope
NBER Working Paper No. 18436
Issued in October 2012
In many education and work environments, economic agents must perform several mental tasks in a short period of time. As with physical fatigue, it is likely that cognitive fatigue can occur and affect performance if a series of mental tasks are scheduled close together. In this paper, we identify the impact of time between cognitive tasks on performance in a particular context: the taking of Advanced Placement (AP) exams by high-school students. We exploit the fact that AP exam dates change from year to year, so that students who take two subject exams in one year may have a different number of days between the exams than students who take the same two exams in a different year. We find strong evidence that a shorter amount of time between exams is associated with lower scores, particularly on the second exam. Our estimates suggest that students who take exams with 10 days of separation are 8% more likely to pass both exams than students who take the same two exams with only 1 day of separation.
