Speaking as an elementary teacher, I can tell you that it's definitely helpful when parents back you up and follow through with consequences and "talks" at home. It's important to communicate with the teacher about what kinds of consequences or rewards you are using at home, because sometimes the teacher can use that as a little private reminder in school if he's starting to have a "bad day."
Besides giving consequences for bad reports, it's important to give some rewards (not necessarily material rewards...let your child choose the dessert or meal that night, give a few extra minutes of play time, etc.). Make sure you're in touch with the teacher so you're only rewarding for actual good days. Some teachers only contact home when things were REALLY bad. They may feel bad writing notes home every day so they pick and choose when they write a note home. Therefore, don't assume that no note means "great day".
I had a general behavior management system I used for the majority of my class (the card system, if you're familiar with it...they started out on a white card, then flipped to green for warning, yellow for first consequence and red for second consequence and contact home).
For some children, this system wasn't as effective. Occasionally I would make an individualized behavior management plan for particular children. This would usually be a chart with a few goals and a few rewards / consequences. Instead of only having one chance all day to have a "good" report (white card) they had a spot on the chart for each hour where they could get a happy face, straight face or sad face. At the end of the day we'd tally up the points and give a reward or consequence if appropriate. The chart went back and forth between home and school each day, with parent and teacher initialing. This was a quick and easy way to communicate (there was also a comments section on back).
PM me if you'd like and I'd be happy to share the chart with you. Of course it's really for use during the school day, so you'd have to show it to your child's teacher and ask if she'd be willing to use it. Most teachers would be willing when they see that you're working with them to try and correct your child's behavior. Things go a lot more smoothly when teachers can see that you're trying to work with them.