In the exam you'll be expected to answer questions on the subjects you studied in class, which means you'll need a full set of notes to revise from. If you missed some classes your notes may not be complete.
To make sure your notes are up-to-date, check your notes against the subject revision checklist given to you by your teacher. If the checklist shows you are missing notes on some subjects, ask your teacher which chapters of the subject text book you need to read and make notes on to fill in the gaps.
