<p>I have heard that at Tufts most classes are taught by TA's because the professors are busy doing research, have other jobs in private industry, etc. Also since it isn't just an undergraduate school, the graduate students take the interesting research positions.</p>
<p>All classes are taught by professors, though lab sessions and recitations are run by TAs. The only time you'll have a TA teach a class is if the professor allows the TA to hold a lecture specific to their research (which only happens once per semester, if that).</p>
<p>I have never had a class taught by TAs, except for a few instances which so<em>ein</em>quatsch mentioned. I had a few classes where once a week, we would have recitation with a TA, but the main classes were taught by the professor him/herself. I had one class where one time, the TA taught because his specialty was the subject matter being taught that day (and he was great!). Other than that, I have only had professors teach, and most of the time my TAs haven't had a big presence (though I don't take many science courses, so I don't know if it is different at all in those subject areas).
Whoever told you that was lying, or talking about somewhere else.</p>
<p>Sam totally hit the mark. I've only taken 3 science courses (whoo, go art history major) and noticed that chem or bio TAs have even less presence than in an art history course.</p>
<p>It frankly scares me that you've heard that classes are taught entirely by TAs. Where does this misinformation come from? The only time a TA has taught my class is if the prof had an emergency and didn't want to cancel the lecture.</p>