As far as I know, I'm pretty sure that they can grow long hair!
I heard that some schools require the young women to keep their hair at a very short length. Whether it's for hygienic reasons or just another aspect of uniformity and lack of attention to hair, clothing, and makeup, I'm not completely sure. Maybe a little bit of both.
Just a personal anecdote, one of my friends keeps her hair short because she said that it's so difficult to manage longer hair. Watching her use relaxers constantly, I completely believe her! The texture is so thick.