Is it permissible to benefit from school notebooks taken from someone who works in a school, knowing that these notebooks were designated for students and were not fully distributed?

There is no harm for you in benefiting from the notebooks as long as you do not know that the man took them unlawfully. The basic principle is that what is in the hand of a Muslim is his property, as Ibn Taymiyyah said: "The basic principle regarding what is in the hand of a Muslim is that it is his property." However, if the matter becomes ambiguous for you in the future and your suspicion of their unlawfulness strengthens, then avoid them, based on the saying of the Prophet, peace and blessings be upon him: "Leave what makes you doubt for what does not make you doubt."