This is required, especially if you have bulk uploaded students and these have been set to the default "unassigned" class. To assigned these students to a particular Class and Section, do the following:

  1. Select all the students you would like to assign a Class/Section.
  2. The Action button automatically displays all available actions. 
  3. Select the action "Assign".
  4. From the pop up, chose the Class and Section you want to assign these students to.