It's important to bring a good backpack on your first day of school. Your backpack is essential for hauling around all the important things you'll need for class. A good-quality backpack can be used to carry your textbooks, notebooks, pens, pencil, calculator and anything else you need for class. Choose a backpack that has plenty of organized storage, rather than one where everything is thrown loose inside. Chances are you'll receive class textbooks and handouts, and it's important to have a backpack in which to carry everything.
Even if your school requires a certain number of notebooks, it never hurts to carry a couple extra. You may want to take your own notes in a notebook that you don't use for a particular class. Notebooks will be an essential part of your first day. Most classes will require you to have them, and you'll need them for assignments. Some teachers will ask you to leave the notebook in class or to use one notebook for that class.
You can never have too many pencils, and like the notebooks, it's a good idea to bring more pencils than is required on your school list. A pencil sharpener and extra erasers should accompany the pencils. Pencils are much better than pens because you can erase mistakes.
Even if your first day is a partial day, you'll be starving halfway through and at the end. Bring money for the vending machine even if you brought your lunch or plan to eat a hot lunch in the cafeteria. It's also nice to leave the school campus to eat out (if this option is available to you), but some students are too nervous to leave school for fear they won't make it back on time. Regardless of what you eat for lunch and where you eat, make sure you have plenty of money to buy what you need.