I have found some grammar rules doing Google search and found a rule about collective noun:-

Collective nouns such as team and staff may be either singular or plural depending on their use in the sentence.

Examples:
The staff is in a meeting.
Staff is acting as a unit here.
The staff are in disagreement about the findings.
The staff are acting as separate individuals in this example.
The sentence would read even better as:
The staff members are in disagreement about the findings.

Do we see this getting tested in GMAT? Or is "collective noun"always singular?