I recently came across this GREAT essay about the Great Schools Ratings and how they can affect continuing segregation in cities. Go ahead and read it and I'll tell you about my own experience.

I live in Portland and PPS has some crazy issues with their boundaries. We have a school that is consistently rated a 10 and the homes around it are some of Portland's priciest. When PPS last proposed a big redrawing of our boundaries towards the beginning of the 2017-2108 school year (as part of a larger restructuring of K-8 to K-5 + middle schools), some schools with large (and admittedly questionable) boundaries went up in arms at the thought that their kids would have to go to a "lower rated" school and feared their property values would drop (note: no boundary changes ended up happening).
Is that crazy? I mean, I'm sure many of us can relate to that fear. But good god, that's pretty sad. Years and years of horrific redlining in our past has made it extra difficult for historically underserved people from moving out of poverty. The schools in their boundaries can suffer too. One school has such a small boundary, that I came to discover that our ENTIRE school would have room to move in. SERIOUSLY? That is truly aberrant.
But people are scared to change - they fear the low rating! As an over-achiever myself, I want to get an A - I want a 9/10, right? A 1-4 is failing. And this is why the essay is so important to learn the WHY behind the number. And furthermore, we are all much more than a number.
When we purchased our current home, our child would be starting Kindergarten that Fall - so schools were of great importance. We realized we were loving some homes in an area where we knew nothing about the school. So we visited. We loved the principal and we saw him greet every single student he encountered by name. That was quite impressive to me. We saw friendly faces and lots of colorful signs and artwork. We saw kids hard at work and playing hard. We loved it! It just FELT right. And guess what? It was rated a lowly 4 on Great Schools. But after our tour and great chat with the principal - we were convinced that this was the school we wanted to attend.
We are now finishing our 5th year at this school. We've gone higher in the ratings (up to a 9!!) and back again to a 6. We don't really pay attention to that number any more because we know we are involved with an incredible community, our kids are doing great, the teachers are fantastic and the kids love their school. Isn't that more important than a number?
As a Realtor and a Mom, I would encourage any family to visit the school - see the kids and teachers in action, talk to the principal - get a feel for the place. And if it feels right - than ignore the number (it's bound to change anyway!).