The third grade uses an A, B, C, D, F grade scale.  Pluses and minuses are also used.
        
The following is the grade scale* for grades 3-12:

             100-98    A+
             97-93      A
             92-90      A-

             89-87      B+
             86-83      B
             82-80      B-

             79-77      C+
             76-73      C
             72-70      C-

             69-67      D+
             66-63      D
             62-60      D-
             59 and below  F

The Norton Board of Education recommends the following homework schedule:

K - 1      10-15 minutes, or more time if necessary   

2 - 3       15-30 minutes, or more time if necessary

   4         30-60 minutes, or more time if necessary

If your child is taking much longer than the recommended time on an everyday basis, a conference should be scheduled to discuss strategies to use class time more effectively.