This will be due to your school's previous Management Information System not rolling up off-roll students one year group during each Year End Process, so the data has migrated over this way.
Students then remain fixed in a particular year group. ScholarPack includes all off-roll students in the process of rolling students up a year, placing students in their correct date of birth academic year group.
If your Head Teacher emails email@example.com from their official school email account, requesting ScholarPack to place off-roll students in their correct date of birth academic year, our Technical Team can action this for you. When you run a report for last academic year, those Year 6 leavers from last year will come up as now being in Year 7, and those leaving the previous year as Year 8 etc.