It is only a pointer, don't worry. It's a pointer that points to pointers.

The struct declaration indeed only reserves one pointer, not an array or anything.

However, I guess you want to have *students in your struct. An "array" of students, right? That makes a bit more sense than what you have now (which resembles a 2D array of students).

Yes, if I've understood properly, for my purpose it's enough an "array of students", I only want to list the students in the school with their exams.
Now, I'm asking myself, why in the spec, that was given as a hint for implementaion, there's such a double pointer variable, is it somewhat better, for ex. more flexible or efficient?

Not in any imaginable way if you ask me. Like I said, a pointer to an array of pointers (an array of "arrays") resembles a 2D array. Unless you want that, there's no use for a double pointer.

You can always create the double pointer at any time by &students, so if the need would arise it has a simple solution.