Why was Marji’s generation so rebellious?

Marjane says that the reason they are so rebellious is that “our generation had known secular schools.” Marjane’s mother and father become defiant as well. The principal simply tells them that they must obey or they will be kicked out of school. When the principal tells the parents to make sure the girls wear their veils correctly, Marjane’s father angrily tells her, “If hair is so stimulating as you say, then you need to shave your mustache!”