Publish Content in Drupal by One Editor Only
As far as i know, Workbench moderation module works based on user roles. The permission to change the state from needs review to published can be given to one or more roles. It is not possible to give permission to specific person.

In your case:


Create a new state 'Ready to Publish'
Add two state transitions, Needs Review -> Ready to Publish and Ready to Publish -> Published
Make sure you remove the state transition Needs Review -> Published (Or you can revoke the permission for this state transition to editor role)
Create a role called 'Publisher'
Assign this role to second editor
Give state transition permission Needs Review -> Ready to publish to editor role
Give state transition permission Ready to publish -> Published to editor role.


With the above steps, teacher posts the content which will be in needs review state. Editor can review the content and can change the state to 'Ready to Publish'. Now, the second editor who has the role 'Publisher' can review the content and can publish.