Extra question for specific students on test/quiz While this may seem unfair intuitively, I want to know whether if it is fair for a professor to have an extra question for specific students in the class.

A little background: In a calculus class, 3 out of a 16 ish students have taken calculus before at their high school, but the university requires them to take a similar class as per the university's rules. The professor knew that they had calculus, and so, during a quiz, he assigned them an extra question, and everyone else didn't have that question on their paper.

Now, it wasn't an extra credit problem, yet, it was graded as a normal problem.

So my question is, can the professor exclude those specific group of students and assign them an extra problem on a test or a quiz?
The goal of any kind of assessment in teaching is to check if each student has met the learning objectives of the teaching activity, and the test should therefore have essentially the same questions of the same level of difficulty for all students. Otherwise, we would ask more of certain students in order for them to have met the learning objectives.