What is the difference between renew and upgrade?

When you renew, you keep using the same books, the same files etc. After all, the kids move up to another grade so for them it is new.
50% discount applies to the licence fee.
When you upgrade, you receive new books and a new CD with the latest issue of the curriculum. Uninstall the old one, install the new one and return the old books to us for disposal. 20% discount applies to the licence fee.
But whatever you do, you need to keep your licence current.