You know those you people who you think don't give a sh!t about life? Well, think about it. Do they really care about stuff. They may have a sucky life at home. Or nobody taught them how to care about grades, manner, and etc.
Have you seen the kid that makes fun of everybody is having a really tough time in life? Maybe they don't care about school and grades because they know won't make it through? They probably think they are stupid. Then people make fun of them.
[This sounded why-- better in my head.]