Studying in a classroom with a female teacher

definitely. First, this is not a problem of modesty in the reasonable norms of our time, and the question of contemplation remains. If contemplation occasionally passes, it is difficult to see it as a prohibition. It is part of life. If it is bothersome (does not leave you) then, in my opinion, there is no halakhic prohibition. It is not possible and it is not intentional. But of course, in the latter situation, even without a halakhic prohibition, one should consider not entering this situation. But an education in which a reasonable person develops bothersome reflections in such a situation is perverse. The obsession with modesty itself is not modest. There is common sense and a reasonable world, and the Torah should be applied within its framework and not in monasteries.