What is incumbent upon me regarding the non-distribution of a portion of the worksheets I photographed at school during my practical training period?

You must seek Allah's forgiveness and repent for your negligence in carrying out your work. If it is possible to return the papers to the school so that new students can benefit from them, that would be a correction of the mistake. However, if returning them offers no benefit and you wish to donate the value of the papers that were not distributed to the students, then that is a good deed, for Allah Almighty says: "Indeed, good deeds do away with ill deeds," and the Prophet, peace and blessings be upon him, said: "Follow up a bad deed with a good deed, it will erase it."