To create a report showing the destination schools for last year's leavers go to Reporting>Reports>Students (tab)>Admissions & Leavers.
Enter the dates for the previous academic year. Then select Former students, Departures and choose their current year group from the dropdown (e.g. last year's Year 6 will now be Year 7):
When you run this report there is a column for Destination School, and the report can be downloaded to Word, Excel and PDF.