There's a tv commercial still making the rounds (it's almost a year old) where the husband suggests to his wife that they not consider a home where the school rating is too low. There are any number of web sites which carry home listings for sale that also provide information from various school rating sources.
Ironically, in San Francisco, this seems to be less of a consideration since proximity to a school is only one of several criteria that determines how students are assigned to schools. Ironic, because one of the most often stated reasons for parents with young children leaving (or avoiding) San Francisco is because of the arcane school selection process. I've seen this countless times both from parents moving to the Bay area for work reasons as well as parents currently living in the city who make plans to move to a nearby county for "better" schools or more certainty in the school assignment process.
There is some suggestion that on-line school ratings somehow undermine fair housing laws.
Inman news has a four-part series exploring this issue. Here's a link to the third in the series.
As with the wide array of statistics available to prospective buyers including recent sales prices, estimated value, crime rates and even investment potential (yes, there's a web site that attempts generate a single number to compare investment potential), it's important for the consumer (buyer) to have an understanding of the underlying meaning. There's a great example of this in an article written by Heather Knight who was the San Francisco Chronicle housing writer at the time -- San Carlos has four elementary schools all of which rate well above the state averages yet some buyers shun the area around the lowest scoring school. In addition, if you delve down into the details of the score you'll find that the high performance in all four schools is coming from a particular racial group with other racial groups well behind their state-wide peers.