Some kids just can't be saved.
There just isn't a place in our schools for bullies, drug dealers or those that intimidate or assault teachers. While every kid should be given an opportunity to change, we need to ask ourselves, do we need to give them a place to hang out during the day and cause problems while endangering other students? The answer is no.
If they don't want to be at school, the school shouldn't be forced to keep them. And yes, that means public schools should be able to expel these students.
There are virtual schools on the internet -- schools that provide lesson plans and opportunities for students to learn the basics but don't have the social interaction with other students. Many of the more troublesome kids may very well do fine with an internet based school. They may even thrive in that atmosphere. But then again, some will show the same lack of commitment to their own betterment that they have in the classroom.