I agree with MLP and Patricia. While my son(16 now, 15 during diagnosis journey) was going through the process of being diagnosed the curriculum director set up an emergency 504 and it allotted for C to have until the end of the grading period to make up work from absences. In the beginning, I thought it would be just what he needed but he is a teenager and he needed structure, with all that time he procrastinated when he was feeling well(he is an honor student and I think he thought...aww no problems I'll just bang it out)and then would be overwhelmed when faced with the amount of work. Also, he was taking tests that were several chapters behind where he was in class because the teachers were not worried about these grades until the end of the period when they had to have all their grades turned in.
Once diagnosed they set up the 504 plan to be more structured as far as make up work and tests/quizzes and projects(but can be altered if absences are extensive), I think C really needed this structure and it kept him feeling connected to the work going on at that time in the classroom.