Students can be pre-enrolled within ERN. These students can then be activated on Sentral using the pre-enrolments process within Attendance.

Once activated, they will then be visible within Sentral.

On the 1st day of student's official attendance with the school, you will need to change their enrolment status within ERN from pre-enrolled to active. Once this has been done and a Data Synchronisation run, the;
Attendance -> Attendance Administration -> Pre-Enrolled Students listing will become empty and the student's actively enrolled within the Sentral Data Layer.

You will need to also include these students in your Timetable Package.