Can you all help me get a little perspective here?

Today my students took the End Of Course (EOC) assessment for algebra 2. Last week my AP stats students took their AP exams.

Last week I knew before they left me that getting half of the multiple choice questions right and about half of each free response questions correct would mean they passed the course and earned their college credit.  Fifty percent was perfectly acceptable and within the reach of the vast majority (if not all) of my students, even though they did not have to choose to sit for the exam.

Today I sent my students into a testing situation encouraging them to do their best.  The scores were available immediately and my highest score turned out to be  student who got 39 out of 76 questions right.  The grade equivalent my central office sent informed me that this student would get an A, 92% on his report card.  I was mad.  I could not understand how getting just barely 50% of the problems right earned a student an A.

Why do I think this is acceptable in one situation and yet am angered in the other? Neither is really making sense tonight.