Book That In allows you to add unlimited staff members to your account, and give them different access permissions. 

Role Permission Options include:

Limited: Access to their own work calendar, but nothing more.

Booking Admin: Access to their own work calendar, plus the Group Overview (inc. attendance registers and Group Event edit permissions). They will only see Group Events for which they are the linked staff member. This level doesn't allow access the Clients area.

Company Admin: This gives full access, the same as main company owner.

Tip: if you don't need to give your staff access to your company data, you can add them but leave the email blank. You can then assign them as the teacher for their classes/events but they won't have access.

This video explains how to set up staff or teachers on your account: