If you use a browser, tabs can sometimes get out of control. I knew I had a problem when I installed an extension that would give me a count of how many tabs I had open in Chrome. When I hit 86 tabs across 5 windows, I knew that there was probably a better way. One of those ways is to use Workona.
Workona allows you to set up groups of tabs per task, and switch between those tasks quickly and easily. Each of these groups of tabs is called a workspace, and on the free tier Workona allows 10 workspaces. For a teacher, this means you could set up a workspace for each class you teach, with the sites you need for that class in one place, separate from another workspace for sites such as your gradebook and email.