Answer:
This argument is an example of a fallacy of composition.
Explanation:
The fallacy of composition is a fallacy that occurs whenever it is admitted that what is true for one part of the system is then true for the whole as well. We can take as an example the case described in the question above, where the headmaster of a high school assumed that the bomb threat in his high school was made by a student who did not study enough for an exam, because in many schools, students who did not study for their exams made bomb threats.
