The Campus license is an educational license giving schools and students access to a network installation to be installed on computers in the school network, but also a standalone option that can be distributed to the students to be installed on their personal computers or laptops.
This means that the school will be handed two different serial numbers:
SolidWorks Education Edition: This is the main serial number for the school, and should only be known by the IT administration. It can be used for downloading the installation files from SolidWorks Customer portal, and to activate the network installation at the school.
SolidWorks Student Access: This is the serial number to be distributed to the students for the standalone installations. It is only valid for one school year, and a new number will be released each year. This serial number will activate the installation but not give access to download from the customer portal.
Since the student do not have access to download, the school administrator should perform a complete download of the installation files and distribute them either from a location in the school network accessible for the students or by using USB-memory sticks or on a DVD.
SolidWorks does provide a media kit if wanted, but that contains only the first release of the Version available. If you download you will get the latest service pack available.