Both of my daughters wear glasses, well, my eldest has just moved into contacts and loves them (age 13). Martha wore glasses from about age 8 onwards, for precisely the reasons you mention: short sighted, can't see blackboard, etc. At first, it was just for this reason, then within 3 years, she needed to wear them all the time. It never bothered her at all. Her friends just saw the glasses look as being a part of Martha, and since she was always part of a brainiac group, she fit in and no-one has ever teased her or made her feel self-conscious about it. She is a neat freak and never loses a single thing, so losing glasses was never a problem with Martha.
My youngest has worn glasses in the classroom and to watch movies for the last 2 years and looks great in them. We deliberately spent the money on a great pair of frames in a colour that suits her and as a result, when she wears them, she looks so great, like a scholar, and I always compliment her. Again, no self-consciousness was ever an issue. She, however, loses stuff all the time. So the solution has been to buy her a real funky glasses case that she would be upset to lose, regardless of the content! Also, she has a particular pocket in her backpack that is just for the glasses case, so we observe the ritual of making sure they get placed back in their case and in the backpack as soon as she is done watching a movie. As a result, we have never lost glasses, only a glasses case once. I consider myself lucky!!!
Yes, get polycarbonate lenses, especially if your girl plays sports.
Hope this helps,
Clare