If you wish to test your student data import file, you may temporarily unmap your headers as follows:
1. Go to Site > Settings > User Imports
2. Under User Import Settings, make note of the Email Header and UID Header current settings. You may consider taking a screenshot to document these settings as you will need to set them back exactly as they are once you are done testing.
3. Click into Email Header, and select the "blank" option
4. Click into UID Header, and select the "blank" option
5. Click Update Settings
You have now unmapped the UID and Email headers, both of which the system needs to map import data into the system. This way, you can see the results of your import file without affecting current import data in your system.