After you have created an Assignment, Assessment, Discussion Board or other item, open the item settings from the Syllabus page to assign settings to specific groups. From here you can apply settings to one group, several groups or all groups. Click Done to save. Students in the appropriate groups will now see the due date, visibility, point scale or other setting exactly as you set for that group.
Groups can be very useful particularly on open discussion boards. To assign groups to a Discussion Board, open the item settings and select the desired Group Set in the Discussion Board Window, from the Student grouping box.