The site you should visit to see published API scores is http://www.cde.ca.gov. Here you will be able to see the Campbell Union School District. It is a great source; however I must concur with CJ below that parents from the area are a great source because they can look beyond the test score. Campbell Union School district is a decent district.
A couple of good site to evaluate schools...
Of course nothing beats talking to parents from the area school you are interested in because they will be able to tell you more than the test scores can tell.
I agree with the others that the best thing you can do is talk with the people in the neighborhood. I live in Downtown Campbell and know the specific streets in and out. I also know a lot about the schools specific to each neighborhood. I would love to tell you more about Campbell, the schools and the community.