The easiest way to add a large number of students, such as a class, is to export your current data from Wixie's admin and then add the new users to the bottom of that CSV file. This will ensure that you have the most current CSV, with any changes that may have been made manually.
***MAKE SURE YOU GO TO THE BOTTOM OF THE CSV FILE!!!*** Do not skip a line and do not erase any of the current users, unless you want their accounts deleted.
Enter the new student information, along with their class information, and then the teacher(s) for the class. Once the file is complete, save it as a CSV file, go back to your Wixie Admin Account, upload the file. It will process at midnight, unless you select process now. Check back for any errors and if there are any, make the changes.
Otherwise, happy creating!
Here is a video on how to add classes to Wixie: http://youtu.be/_Wqj5Hcnkt8