Data about everything from fees to college grad rates are available at an excellent website hosted by the National Center for Educational Statistics and called the College Navigator.
Colleges and universities report their data based on "first-time full-time" enrollees, which means that students in a particular high school class who enter college as full-time students for the first time in the semester after graduation are tracked. The NCES provides four and six-year college grad rates for every college that takes federal funds.
We've used the same statistical calculations to track Boise District students for the past six years, and we now have complete six-year data for the 2007 Boise District high school graduating class. It's interesting that the highest percentage of Boise District college grads major in Science, Technology, Engineering, and Mathematics.