New England Tango Academy

I found beginner Tango instruction by William Chen to be clear and engaging. His classes are a great way to start appreciating tango, learn basic posture, embrace and most fundamental steps. William takes care to emphasize different fundamentals on consecutive beginner series, so taking several classes one after another does not get tedious. His approach to teaching is very methodical, he breaks down to most basic elements, and takes care to address biggest mistakes one at time, without attempting to get to the perfect form with infinite corrections that could easily confuse a beginner. After classes, there is usually additional time to practice. One minor and very subjective gripe is that William’s teaching style is more mechanical than passionate, yet it works very well to get one comfortable on the dance floor.
Boston has a great tango community, and once you are addicted, beside NETA there many excellent studios with different teaching styles, but NETA is great place to start and advance your tango skills.
I must note that studio description on Unilocal is somewhat out of date, since the founding instructor, Fernanda Cajide, has moved to Barcelona in 2011.