I am not sure of how the grading system worked at his particular school at that particular time, but it would appear that JFK received numerous C's and D's during high school (see: scores in the 60s and 70s on page four).
Ah, I see now. Page 6 appears to be the results of an exam conducted by Harvard, and I had figured Page 4 was probably related (in which case who knows what a "good" score is).
Now, the other question, how much did academics matter in 1935?
While JFK's grades may have been unexpectedly poor in any case, readers should bear in mind that C and D had different meanings than today's due to grade inflation.
