teachma is right. I don't have a reference, although I've seen them (dh is a hs teacher). The average income in a district is a key predictor of how well students do on standardized tests. Get your state's "report card" for the schools in your area and you'll probably see the pattern right off.
I do think test scores are one measure and are a measure I'd look at. But they aren't the be all and end all. I'd look at class size, philosophy, look at what happens with graduates of a district, programs offered, etc.
Obviously, what matters to one person might not matter at all to another. Academics are very important to us, and most other things are a distant second. I don't give a hoot how the district's high school's football team does, but I've actually found parents who care about that kind of stuff.
My dd will also be entering 1st grade next year. I've been very happy with her public school so far. It's a very good district--that's why we live where we do.
They do some stuff about testing which I'd find annoying if I took it seriously. I actually had dd's kindergarten teacher tell me how to get her to analyze books she's read with an eye on how questions are asked on the 3rd grade language arts exam. I burst out laughing and told her that I'm not going to suck the joy out of reading for my kid and that she and I both know that the kids will do fine on said exam without all the extra coaching since she has the right demographic. She basically admitted that was true.