As the board isn’t yours @Virginia A Black , you wouldn’t be able to delete it but you could leave it by accessing the “...” menu in the Miro dashboard:

Kiron

when I click that button, there is no option to leave the board. no idea why-

thanks

@Virginia A Black -

The workaround would be for the student to remove you from the sharing list for that board - can you ask them to do that?

Kiron

@Virginia A Black, 

Here is an excerpt from the article How to Leave a Board:

I don't have the Leave board button, what should I do? 
- If the board is inside the Free plan account, it will be shared with the team by default as the board privacy feature is unavailable on Free plan. You can upgrade your team to create private boards. You can also sort your boards by the board ownership (please check these guidelines).
- Please check your ownership of the board, if you are the board owner, you will see the Delete button instead. 

I hope it will help!