Does signing attendance on behalf of another in lectures fall under forbidden lying, and does it make the money earned after graduation unlawful?

A student signing the attendance sheet for her absent colleague falls under the categories of lying, forgery, and betrayal of trust, all of which are forbidden. The Prophet, peace and blessings be upon him, urged truthfulness and warned against lying, for "Truthfulness leads to righteousness, and righteousness leads to Paradise," and "Lying leads to wickedness, and wickedness leads to the Fire." If this signing results in the student obtaining grades or an evaluation she does not deserve, and she then uses this to secure employment, then this is considered unlawful gain; because what is built upon falsehood is false. Therefore, students must be truthful, avoid lying and forgery, and steer clear of favoritism in forbidden matters.