It is crucially important to keep your important documents and files backed up. The computer on one's desk should never been considered a permanent storage location. Below are some backup options for your consideration.
Small Backups: If you have a limited amount of school related documents that you need to backup then your P: drive is a great option. This area is access controlled so that only you will have access to these files. Any school computer that you login to will have access to this drive.
Small to Medium Backups: If you want access to your data anywhere then using OneDrive for Business which is included in your Office 365 account is a great option. Just be aware that this will require all of the data to be uploaded to the Internet and this can take some time. In OneDrive your data is still access controlled to be only available to you but can be shared to other users and accessed anywhere with Internet access.
Large Backups: If you have a lot of data including pictures, videos or music that you want to backup then an external hard drive is a good option. These are available pretty inexpensively at Walmart, BestBuy, Amazon, etc.