Hello Ralph.

You could use a function like this (in a standard module):

Option Compare Database
Option Explicit

Function SchoolYear(Birthdate As Date) As String

   Dim September1st As Date, Today As Date
   Dim Birthday As Date
   Dim AgeOnSeptember1st As Integer

   Today = Date
   September1st = DateSerial(Year(Today), 9, 1)
   If September1st > Today Then
       September1st = DateAdd("yyyy", -1, September1st)
   End If
   AgeOnSeptember1st = DateDiff("yyyy", Birthdate, September1st)
   Birthday = DateAdd("yyyy", AgeOnSeptember1st, Birthdate)
   If Birthday > September1st Then
       AgeOnSeptember1st = AgeOnSeptember1st - 1
   End If
   Select Case AgeOnSeptember1st
       Case Is < 5
           SchoolYear = "too young for school"
       Case 5
           SchoolYear = "Kindergarten"
       Case 6
           SchoolYear = "first grade"
       Case 7
           SchoolYear = "second grade"
       Case 8
           SchoolYear = "third grade"
       Case 9 To 17
           SchoolYear = CStr(AgeOnSeptember1st - 5) & "th grade"
       Case Else
           SchoolYear = "too old for school"
   End Select

End Function

You could use an expression similar to this as the Control Source for a
textbox on the form (I'm using generic name for BirthDate field, which I
assume is in the form's Record Source query):

=DateDiff("yyyy",[BirthDate],DateSerial(Year(Date())+(Format(Date(),"mmdd")<"0901"),9,1))-5

You will get a 0 from the above expression for Kindergarten grade. If you
want to show Kindergarten as the grade in that situation, use the text box's
Format property:
   ;;"Kindergarten"