Student or Learner
Which is correct,
Staff (meaning human resources) is
Some people are more likely to think of the staff as one unit, operating together, and use the singular.
Some people are more likely to think of the staff as many individuals, and so they use the plural.
(I assume you mean the people who work somewhere, and not the thing that you picture Gandalf holding in his hand, right?)
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.