Now cheating is always a possibility but there is also a luck factor. Maybe this year the subjects covered happened to intersect with the questiosn asked a bit better than most years.
Also look at the numbers. Micro economics is an easy test to get a perfect score. In general you are looking at 109/2.2 million. But in Microeconomics you are looking at 33/67k. ABout 1/3rd of the perfect scores come from microecomics depite it being like 1/30th of the tests given.
Throw in this is some 38k/yr private school you are not looking at a normal population of students.
Here is another article : http://www.mercurynews.com/ci_24616918/monta-vista-seniors-find-perfection-ap-computer-science?IADID=Search-www.mercurynews.com-www.mercurynews.com where 3 kids from the same score aced the AP computer science test. 3/19 in the same school is also something that you don't think should happen.
But when you have large sample sizes, you will often get odd results.
The article isn't very well-written.
Reading it closely, I think all 11 of the students in the class got a 5 out of 5. That's what they are calling a 'perfect' score.
They didn't all get every question correct as the article goes out of its way to mention the one student who got all the questions right and differentiate that person.
My senior year AP class had everyone get a 5 out of 5 on the BC calculus exam. We had 10-15 kids in the class.
Our teacher did consult for the AP so she knew what to teach us but there was no cheating involved.