To enable Class Charts to display attendance you need to go to 'School settings' from the three lines menu in the top right hand corner of Charts Charts and choose 'Modules' from the left hand side of the page.
You can set one of three settings.
1) Disabled (no attendance information is pulled through or displayed)
2) Enabled (designed for primary schools, can take attendance in Class Charts but is not written back to any MIS)
3) Display Only (Class Charts will pull attendance information through from SIMS and display it in class and pupil reports, not designed for taking attendance)