If I was another student, the motion of you standing up would draw my attention, but after an initial glance, I wouldn't have done anything. If I was the teacher, I'd probably ask if you needed something, thinking you might have stood up to get my attention. If you replied that you were just stretching or something, I'd go about class as usual, as if you were still sitting. In either case, I'd probably assume that you'd been sitting funny and got a cramp or sore joint that needed to be straightened for a little bit. That can happen to anyone, especially after long periods of being in the same position.
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Yet in my new wildness and freedom I almost welcome the bitterness of alienage. For although nepenthe has calmed me, I know always that I am an outsider; a stranger in this century and among those who are still men.
-H. P. Lovecraft, "The Outsider"