If you'd like to remove the Skillpower quiz you can remove link to the quiz that is sent in the New Client Welcome email under Transactional Notifications.
Follow these steps to remove the Skillpower quiz from the initial account creation email:
Select Business Settings
Choose Transactional Notifications
Under the section titled clients, expand the Sent when a client has completed creating their account email
Remove the [skillpower_url] from the text body
Select Save