other team members' boards are in my account

​@Patricia Childers if the restrictions aren’t in place at a team or organisation level, then it’s easy to unintentionally invite people to the team when sending a link to a board. Best practice is solve it with admin settings.

As a team member / team admin, be deliberate about settings, before sending out links.
Every-time you send a link
• Check the access permissions, before sending, to ensure you’re only sending guest invite links.

As an admin, adjust “Who can Invite” settings
Do it once and done.
Restrict the who can invite people (students) to the team.
• Restrict inviting new people to team owner only
• (or) Restrict inviting new people to company/org owner only

Example settings:

​@Patricia Childers - Team/class members may have previously signed up for Miro via a team invite link and they may not have their own space to create their own boards. It's really hard to say without knowing anything about your (or their) account setup/type. 

If you have and Education Plan subscription, then the Guest feature (for editing) will not be an option for you. Instead, you'll need to use the Visitors feature if you want people to edit boards that reside in your account while not being a team member.

The only way to stop people from creating boards in your team is to remove them from the team altogether.

"If" they have their own team space, you could tell them to create boards in their team and not yours, however, as I mentioned already they may not have their own team space. 

A word of caution when removing/deleting someone from your team: They will lose ownership of all boards that they own and may reach out to you to request a copy of the board. If you anticipate that happening and are willing to oblige their request, you should download backups of any boards before you delete them. However, that person will also need to have either an Education Plan or paid subscription in order to restore the board as Free Plan users cannot restore board backups (i.e., .rtb files).