The new role editor allows you to create custom roles and limit what they can do.
The dropdown will show all the roles you have in your school. You can choose a role to edit it (except admin and support, they are uneditable), or create a new role.
When you choose a role, you can choose exactly what permissions to give them.
Custom roles can be added and deleted at any time. Deleting a role will cause users with that role to not have any special permissions (they will have the same permissions as a regular parent or student).