Okay, I have to first admit that my opinion on this is kind of far out there, but it is based on my experience both as a teacher and as a parent. I taught first grade in a "10" school, and it was the worst school I've ever seen. The parents tend to make outrageous demands on teachers (why isn't my child in the front row? what does he need to do to get a front row seat?), and the pressure to get kids to pass standardized tests has 8 year old kids in tears, with obvious signs of stress (headaches, stomach aches). Were all kids like this? No, but I saw it a lot.
A "2" school is likely a high poverty area. It doesn't necessarily mean the school is worse, but it's still possible. At this point I would want to delve a bit closer at the crime rate for the neighborhood I'm looking at. Your child isn't necessarily going to get a worse education. The lower performing school just means more of the kids at that school are having trouble, not that the teachers are worse. If they are title 1 there may in fact be smaller class sizes, and some REALLY dedicated teachers trying to do the right thing. Like others have stated, you would want to take a tour and ask around. The best indicator of a child's success in school is their family income, not what school they attend.
I currently live in an area where the schools are 5-7. I absolutely love it and wouldn't change it for the world. None of the high pressure garbage, and my children get the right amount of attention and there is very little drama. I also got a much nicer house than if I was trying to find a 8-10 school. If I had to move again, I wouldn't hesitate putting my children in a 2-4 school as long as there isn't a lot of violence and I checked it out first.
I haven't done this in awhile, but I used to get the raw data from school districts and do a scatter plot in excel that compared the % free lunch with student test scores. If you can find a school that shows up above the trend, you might find a diamond in the rough...