You can remove students from your Education studio at any time and reassign their seat to another student or colleague.
To remove a student simply click on Management -> Members and then "Edit"
Next to each member name you'll see a red X:
Simply click that X to start the removal process.
The next step will ask you to confirm you want to remove the individual and what will be done with their files. These would be the files that they themselves created and would not include files created by others and shared with them.
You have the option to let them keep their files; transfer the files to yourself; or transfer them to another team member:
Once you confirm your choice, the student will be removed from your Education studio and will have their own individual account, with access to our Basic plan (unless they chose to subscribe).
You can then add another student to the unoccupied seat.
Celtx in the Classroom article.