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<p>TA is from the country that is the mortal enemy of your own country :)</p>
<p>I once had a TA from Pakistan that managed to wreck havoc on all the students from India (to the tune that the school got involved) in a grad class… Some of the Indian students were friends and they were quite upset. </p>
<p>Another reason - Gender clueless-ness by the Prof’s. This happened to Mrs. Turbo and some of her female fellow grad students… Visiting Prof came from a strong male dominated country and made it quite explicit that he did not believe women could understand the intricacies of theoretical Statistics. He changed his mind after a flood of formal complaints to the school…</p>
<p>Professor teaching at a completely different level than expected… I was taking Discrete Math in section A and a friend in section B with a brand name guy (a genius in the field, except that he looked like Sam the Pirate, chewed tobacco in class and carried a spittoon along - no joke). I copied one of the homework answers from my friend (a problem that not a single student in section B had been able to solve and Prof. Sam solved it on the board) and got it back the next day with a comment from my Prof: “I can’t understand the solution, but it looks correct” :)</p>