Shared Drives and a shared folder in your Google Drive are slightly different.

You can use shared drives in Google Drive to store, search, and access files with a team. Shared drive files belong to the team instead of an individual. Even if members leave, the files stay in place so your team can keep sharing information and work anywhere, from any device. - What are shared drives?

Shared Drives can be found in the left hand column in your Google Drive. Even if you have not created one yourself you will probably find that you are already have access of some Shared Drives.

Where to find Shared Drives

Shared Drives work around 'access levels'. The Head of Department (or Head of Year for a pastoral team) should be the Manager. Staff members should be content mangers. A guest such as a PGCE student should be a contributor.

Appropriate access levels

This useful video from the folks at AppsEvents summarises things well→