Users can determine how a student's age is calculated by setting system wide preferences in Business Rules. For example, you can calculate a student's age as of the first day of school.
In Configuration, click Business Rules and select Student or Applicant.
In the Base student (applicant) age on: field, select Specific Date and enter a date.
The student or applicant ages as of the specific date displays on the Bio 2 tab of the record, in a query, or a report. If applicable, change your Business Rule back to the previous settings, to avoid possible confusion.