I can understand a zero tolerance for sharp knives and guns.
I can understand a zero tolerance for illegal drugs and alcohol.
The permenant marker thing, I think the kid should have had to clean all the desks and/or other items with grafiti to show someone has to clean it off and its not very enjoyable. Let them see actions have consequences. I remember someone had to clean gum off the bleachers when they put gum under a desk. They never did it again.
Inhalers as they are needed should be talked about with all involved, teacher, child, parent, and principal. Parents should inform severity of condition to the teacher and principal and the child should be instructed with all there not to bring it out to show other kids but rather only when he/she needs to use it. Maybe even help provide sugestions where to carry it so other children can't get to it as there are risks to others.
Schools need to work with parents and visa versa.