Rankings are always tricky. Rating the top art schools depends on the criteria of the one or ones doing the judging and possibly whether or not they have some sort of connection or vested interest in placing certain schools where they place them. Cronyism aside and imagining a perfect world of total objectivity, a one-size-fits-all rating system would only work in a world where artists are determined ahead of time in a test tube and everyone is a homogenous clone. But then you have to wonder if art and creative expression would even really exist in such a utopian society.
So, back to the present day reality, a single specific answer to the question, "What are the top art schools?" generally does a disservice to the needs of the individual student. As with stereo components, it depends entirely on priority and application. The top school for music and performing arts will likely not be the top school for commercial and visual arts. Even within a single category, the "best" art school will still depend on the needs and priorities of the student.
There are a number of organizations and publications willing to give it a shot, though, and their conclusions can be easily found on the Internet. However, it is best to consider these ratings simply a starting point, as they can be quite misleading. Remember that higher education is funded primarily by the students who attend said facilities. No students, no school. No school, no over-paid faculty incapable of working in the real world. (Oops. Did I say that out loud?) And that, that certainly does not apply to all art school faculty members.
The first thing you need to determine is what you plan to do with an art education. There are many and varied career choices. The art career or occupation you want will be one of the most important deciding factors in your own personal ranking system.
For instance, if you're already working in the art field of your choice (or close to it) and all you need is a piece of paper, then you can probably get what you need from a local community college or state university. Depending on the state, that may be a less expensive way to get that piece of paper than going to a dedicated art school.
If, on the other hand, you're gunning for a particular possibly prestigious position in a well-known art gallery, it would serve you well to work backwards. Find out what they consider the top art schools and which of those they most often hire graduates from. In other words, which art school degree will get your resume to the top of the stack?
Your choice may also come down to economics. What can you afford; what kind of financial aid is available; and what are you chances of a reasonable pay off?
In the end, you are the judge. You will have to determine what the top art schools are for you and make the best choice for you. After all, individuality is the very pulse of art.