I don't know their situation but back when I was in HS and taking 4 AP classes at a time, that would have been extremely, extremely hard to make up that much work for 2+ weeks of being out. The homework workload is that of a typical college course. And often times AP classes can have a lab component where you need to be there to perform the lab or other assignment (chemistry, physics, maybe even calculus, etc.), so it becomes a logistics problem and not just about spending the time to do the homework. Then it gets even more complicated when you factor in the possibility for exams or other major projects in that time frame. I don't blame them at all for not wanting to miss school. AP classes are also extremely important for college prep in general. Also you have to factor in the mindset change - it can be very hard to get back into the classroom after an extended vacation, especially knowing that you are now behind your classmates and won't be able to use them as resources until you catch up. As much as I love WDW I would NOT have wanted to miss that much class back then, so I can sympathize.