Pre-Employment Check SA - W2 Forms

As a part of the employment check for BB SA positions, are W-2 forms pulled by the verifier? If someone had an on-campus job but was fired from it, can the banks find out about it? Is receiving a payment from an employer sufficient info for a verifier to find out even if you don't disclose it? If so, will they really care about it? Thinking of taking an on-campus job, but might not have time for it.