You can either change a student's position manually or automatically: Alphabetically, by name or by a column (i.e. ranking)
Automatically changing the position of your studentsTo sort automatically, tap on Options (students header) > sort
What does the 'Group' setting meanStudents in a class may be assigned to a group (details here)
The 'Sort by group first' setting will take this group into account when sorting so that all students from the same group are kept together and then sorted.
Here an example:
The first image on the left shows a list of students that has been sorted with the 'Sort by group first' setting disabled.
The image on the right, shows the same list, but with 'Sort by group first' setting enabled.
The group to which they belong is shown below each student.
Manually changing the position of students
How to: add students
Create student groups in a class