It's amazing the number of prominent artists who taught at or passed through the Art Students League on West 57th Street. It's not a particularly prestigious school. Anyone can take classes. My father did in the 1940s, when the Upper West Side was an Irish slum. But just look at this list: everyone from Frederic Remington, Winslow Homer and Norman Rockwell to Georgia O'Keefe, Louise Nevelson, Isamu Noguchi and Maurice Sendak. (I didn't compile this, just counted it. The source is Wikipedia.)
The Art Students League has a big edge because it has been around since the 1880s. Lots of time to accumulate artists, especially early in their careers. It's part of the New York art cluster (hello, Richard Florida). And anyone can take or teach a class. But what strikes me is how much the U.S. art world has not been centered on New York. You've got to go down to No. 8 to find another New York school - Parsons - and the next one, NYU's well-endowed Tisch, doesn't come up until No. 13.
Are Wikipedia entries the best way to gauge an artist's prominence? Sure, as long as you don't confuse prominence (which you can measure) with quality (which you can't). The best thing about Wikipedia entries is that you can count them.