<p>The Course 3 S.M. is “real.” There is a so-called “by-pass” option in which students can be admitted directly to the Ph.d program without getting the S.M. first, but it requires passing generals within a year after admission and taking certain pre-req courses. If you flunk the generals I guess you get a “consolation” S.M. Otherwise you HAVE to get an S.M. before being admitted to the Ph.d program. I got this from the current web site. You probably don’t see too many S.M. students as TA’s because the way course load restrictions work. It generally takes longer in most departments to get an S.M. if you are a TA. Also, most S.M. people are not headed into teaching, so the experience may not be so valuable. The only course I know of in which a Master’s might be considered a “consolation prize” is physics, where they only offer Ph.d admissions. Perhaps there are others, but I don’t think any of the engineering disciplines are among them. I got my S.B. and S.M. at the same time after 5 years in Course 2 (admittedly a long time ago), and became a grad student in what would have been second semester senior year. Though I was offered a TA, I took an RA instead because it saved me a semester (and the net pay was better). The “terminal” S.M. is common in engineering and is not necessarily a sign of an inferior student – just someone who is not heading into academia. After military service I was later admitted to the ME Ph.d program at Berkeley, but ended up at Harvard instead in professional school.</p>