You can obtain an Attendance Report to include in-year leavers, via Reporting > Reports > Attendance (tab) > Custom Attendance Report.
Please refer to - Custom Attendance Report
This report pulls through former students by default, but only ones with attendance codes entered for the date range that you choose. If you choose a date range of this academic year then your in-year leavers will be included. There is also an option to only show data for students on roll the entire period selected.