Something like this maybe?
If the grades are ALWAYS non-formulas, you don't need the second part, but it doesn't hurt
Option Explicit
Sub PassFail()
Dim r As Range
With ActiveSheet
On Error Resume Next
For Each r In .Columns(1).SpecialCells(xlCellTypeConstants, xlNumbers).Cells
If r.Value >= 60 Then
r.Offset(0, 1).Value = "Pass"
Else
r.Offset(0, 1).ClearContents
End If
Next
On Error Resume Next
For Each r In .Columns(1).SpecialCells(xlCellTypeFormulas, xlNumbers).Cells
If r.Value >= 60 Then
r.Offset(0, 1).Value = "Pass"
Else
r.Offset(0, 1).ClearContents
End If
Next
On Error GoTo 0
End With
End Sub