What is the ruling on the money I earned from helping students with their graduation projects, and can I take the last installment due to me, and is my refraining from helping students in the future, whether for a fee or for free, considered withholding knowledge?

Money earned from doing graduation projects for students is unlawful if the work is done in place of the student himself, as it is considered aiding in cheating and deception. This money must be disposed of by spending it on the welfare of Muslims. As for permissible assistance in scientific research, such as indexing and preparing references, it is permissible whether for a fee or not.