Once you've set up your static or dynamic group in Reporting > Data Digger, you can create an attendance report by going to Reporting >Reports > Attendance (tab)>Attendance Percentage Between.
Please refer to:
From the Group dropdown select the Static or Dynamic Group, set the date range then click Choose.
A table will appear with the individual students' attendance figures, with the overall figures in the bottom row.
This report can also be used for Intervention Groups.