You're being silly. "Exceptional" is a relative term. The exceptional individuals in any group are those at the ends of the distribution curve. Operational definitions vary; for instance "those more than two standard deviations from the mean ", or "the top five percent" or "the top one percent" or "those with a GPA of 3.8 or higher". By definition, among the group of computer science students, some will be exceptional. 

I will concede a remote possibility that an entire class of 150 could be composed of mediocre students, when that class is compared with the whole body of students of the subject world-wide, but it seems unlikely unless your operational definition of "exceptional" is EXTREMELY  restrictive.