Before this is ran please ensure your data is sorted first by ID, then by the Term. Also make sure your data tab is named Data as this is what it is looking for in the code.

Next you will need to add a fourth column called Weight to your data converting your Grades to a numeric value representing its Weight. I made a VLOOKUP function where A would show as 13, A- as 12, B+ as 11, etc. up until W as 1. You will want these on a separate tab as we will be deleting rows from the first data and it will break the VLOOKUP weights if they get deleted.

Once you have your formula, copy it down all of your data so each row contains the grade's corresponding numeric weight.

Here is how the data should look: http://imgur.com/cfVZdwq

Finally, this VBA will do the rest of the work.

Public Sub Sort_Grades_Data()
    Dim data As Worksheet
    Set data = VBAProject.ThisWorkbook.Worksheets("Data") ' Worksheet containing data

    ID = 1 ' column ID is in
    Grade = 3 ' column Grade is in
    Weight = 4 ' column with vlookups converting grades to numeric weight

    crow = 2 ' first line of actual data (not headers)
    While Len(data.Cells(crow, ID).Value) > 0
        If data.Cells(crow + 1, ID).Value = data.Cells(crow, ID).Value Then ' Check if the next line is the same ID
            If data.Cells(crow + 1, Weight).Value >= data.Cells(crow, Weight).Value Then
                data.Rows(crow).EntireRow.Delete ' next row has greater or same weight so delete the current row
                crow = crow - 1 ' since we deleted a row, we have to go back one step
            ElseIf data.Cells(crow + 1, Weight).Value < data.Cells(crow, Weight) Then
                data.Rows(crow & ":" & crow + 1).Interior.Color = RGB(255, 255, 0) ' Set rows to yellow
            End If
        End If
        crow = crow + 1 ' move to the next line of data
    Wend
End Sub

Let me know if you have any questions.