I would second those thoughts- I wouldn't worry a lot about grade school grades. We were pretty unimpressed by a lot of the teachers that my older child, now in junior high, had at our highly rated public grade school.
His grades in grade school would vary- he would do the math in his head correctly and get an F because he wouldn't "show his work." He had all A's in junior high this year including taking Algebra I in 7th grade (accelerated 2 years) in the advanced classes, plus being first chair in the orchestra. His 6th grade teacher refused to recommend him for honors math until he took the SAT in 6th grade and aced it, plus he got a 95% on the math placement test (a 75% or better was required to enter the class)!
I would pay attention more to the content of the grades. For example, if it looks to you and the teacher like your child's handwriting is poor, try to work on that at home. Etc.
