You can also ask the school counselor to observe your daughter in the classroom to give you an objective opinion of what she is doing there. If the problem appears to be motivation, the counselor may be able to give your daughter some individual time or include her in a small group on that topic.
If the problem appears to continue when your daughter starts junior high, jump on it early and get her the extra tutoring or counseling that she needs. Both the elementary school and the junior high have screening tests available that you can request to determine how far behind your daughter is.