I'd say your best bet is to visit the school's website, or the State's Department of Education's website for the particular school you're interested in. The Department of Education site is the most likely place to find all kinds of metrics such as high school graduation rates, SAT scores, National test scores, etc. for schools within that state. For example, I google'd for "California's Department of Education", and found the "Testing and Accountability" link, with which I was able to drill down to the school level and find the % of students from my old high school who went on to a 4 year college.