Praise be to Allah.
Undoubtedly a student’s giving a fake signature on behalf of her classmate, to show that she was present when she was in fact absent, comes under the heading of lying, forgery and betraying trusts, and all of that is haraam.
It was narrated that ‘Abdullah ibn Mas‘ood (may Allah be pleased with him) said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “I enjoin you to be truthful, for truthfulness leads to righteousness and righteousness leads to Paradise. A man may continue to tell the truth and endeavour to be truthful until he is recorded with Allah as a speaker of truth. And beware of lying, for lying leads to wickedness and wickedness leads to Hell. A man may continue to tell lies and endeavour to tell lies, until he is recorded with Allah as a liar.” Narrated by al-Bukhaari (5743) and Muslim (2607).
If attendance is part of the grades that are mentioned on the graduation certificate, and success or failure each year, and the type of grade that the student will get, depends on that, then if she attains what she does not deserve of grades or honours, and gets a job based on that, then she is in danger, because that which is based on falsehood is also false. This applies if her absence means that she is not qualified for high distinction, for example and the job was only given her to because of this distinction. In that case, she got the job by unlawful means.
Hence we advise the students to strive to be truthful in recording attendance, and to give up lying and faking, so as to avoid sin. They should beware of getting jobs by unlawful means later on, and they should realise that there is no room for doing favours and bring nice if it involves committing unlawful actions.
May Allah help us all to do that which He loves and is pleased with.
And Allah knows best.