From the grade book view, tap on Tools icon on top right. These tools will let you change the order of your columns, tabs or students amongst other things.
![app store gradebook](/images/idoceo6/gradebook_tools.jpg)
Columns and students can be drag and dropped from the gradebook view. The Tools options are usually meant to do operations in bulk
Here a short animation showing both methods
![teache ipad](/images/moving_students_columns_tabs.gif)
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