Answer:
Hasty Generalisation
Step-by-step explanation:
A fallacy is the use of faulty or invalid reasoning to construct an argument, such a arguments are deceptive as they appear to be better that they really are.
The fallacy in which a person arrives to a conclusion which is not logically justifies by unbiased or sufficient evidence. When a person makes hasty generalisation, he/she applies a belief to large population based on information he has. If my friend likes to eats lots of pizza and is healthy, i can say that pizza doesn't make a person fat and pizza is healthy.
The students mentioned in the question are making hasty generalisation.