Sometimes, you may want one or more of your students to start at a later stage in a particular world, instead of starting at the beginning. You can give them a token which will let them skip ahead to any stage. Here's how to do it.
1) Switch to "List" view
When you're looking at the world you want to open for your pupil, click on "View as list" in the lower left of the screen. This will show you all the stages for the world, presented as a list instead of graphically.
2) Find the stage you want to unlock, and get the token.
Scroll down until you find the stage you want to unlock. Underneath the stage name there will be a token. Make a note of the token. Note that pupils will not see this token: you only see it if you're logged in with a teacher account.
3) Give the token to your pupil(s).
Your pupil can enter this token now, to go straight to the start of this stage. Please note that they will need to be on this world before entering the token, or the token will not work.