Try each of the following steps in order until the issue is resolved:

    1. Review report parameters to include Students marked  as "Left" are included in the report:
    2. On the Format tab of the report, highlight Details.
    3. Mark the Include Students who left checkbox if they should be included.
    4. Mark the Primary alumni information checkbox on the student's education record.
    5. Ensure the parent codes selected on the Filters tab of the report are valid for the missing constituents:
    6. In Records, click Constituents. 
    7. Click Open a Constituent and search for and select the missing constituent.
    8. On the Bio 2 tab, make sure the constituent has the parent code selected on the report.
    9. If Date From and Date to values are specified for the constituent code, make sure it falls within the date range of the report.
    10. Make sure the format of the class year is set to 'yyyy'