My first reaction is the private colleges or universities are better than public schools. Having attended a very good public university and then an Ivy League graduate school, I'd say there is no comparison.
Where do I start? First, class sizes in private schools are significantly smaller, meaning a more intimate learning experience. Professors are better and almost immediately available, especially compared to competing with the throngs of students (these days) in most public schools, where sometimes professors are not available at all, being replaced by the inimitable TA.
I was amazed by some of my graduate experiences, one of which was a class in advanced syntax (grammar) which I shared with nine other students from several other countries. While I learned amazing things from the professor, I also learned so much by listening to the other students. When students come from other countries to study in the US private schools they are usually very motivated, and can provide perspectives and knowledge that is very hard to find in public school settings. To learn in such an environment is wonderful, almost magical.
Many public universities in the US have been increasingly sacrificing quality for tuition over the last 30 years, especially driven by the economic crisis of the late 80s and the one we are currently experiencing (beginning in 08). Once even public schools could afford to have all sorts of smaller programs and specialized classes, but this is mostly history now.
In corporate America organizations are viewed from within as being composed of two kinds of peoplethose who make money and those who spend money. Following on this corporate model means that while some less lucrative programs, like linguistics, still exist, public universities are focused on the 'cash cow' programs like business or computer engineering. Although programs vary as to their earning potential students are the only entities that always add to the bottom line, whereas only some professors bring enough grant money to pay their own way while also bringing in scores of students to take their popular classes. So, students have been courted more and more in the last 20 years as colleges will invest in larger classrooms which generate money, but don't require more professors.
Put these forces in play and my undergraduate university where I had maybe 25 students in an average class (about 1980) now has an average of 150 sitting in auditoriums with a single professor (some classes maybe up to 400 with no actual professor in the room, only video monitors). Let's also add the newest trend in many public schoolsonline or distance learning. Amazingly, costs for many online programs are actually higher than courses in which you actually get to use university facilities. Meanwhile such programs are a goldmine because there is virtually (no pun) no overhead, and costs for educational media continue to plummet. The reality is that huge class sizes and distance classrooms cannot provide a good education for those who need solid undergraduate training. Nevertheless, both trends will continue in public schools, but only marginally affect large endowment private institutions.
Not wishing to denigrate my Alma Mater too much, there are some good aspects to public schools - well, it depends on your attitude. Large public universities are great for parties and for the pure fun of supporting team sports. But, at least as far I am concerned, there was nothing like the intellectual challenges I faced in my private graduate experience. This made me grow as a person and forced me to raise my level of academic achievement. Parties and football games are great, but mostly what you have when they are over is a hangover. The fact is that party schools produce graduates that mostly know how to party, but don't compare well (at the undergraduate level) with the more serious minded private schools.
Finally, having a degree from a private school is usually a predictor of getting a good job. Part of this is because organizations know these students are better prepared and part of it is because private school graduates are better able to compete with foreign students, many of whom are very well educated, especially compared to American public school standards. Not only are many foreign students very solid academically, but they are also hard working and (unlike many American students) very thankful to have opportunities to live, study, and work in the US. I had to work for my Ivy League private graduate school to pay my tuition, but every hour spent doing all those unglamorous jobs was worth it.