Zero tolerance is put in place for the same reason McDonald's started the ordering system #1, #2, #3 and so on for 3 reasons. Because they realized that most folks do the same thing for the same reason, because it saves time and culpability for their employees.. it doesn't require actual decision making or influence on behalf of their distrusted employees.
Same thing goes for zero tolerance. They assume people bring weapons to school for the same reason (wrong! this is a great example), it certainly saved time and didn't rely on decisions of local, distrusted administrators by not having one of the geniuses they hire and promote make an actual judgement call and washed his/her hands of anything of consequence.
Too bad, McDonald's got it right as they also offer customer-dictated options whereas schools don't allow for that freedom within the system.
- Quoted from the comments of an article, "Boy does right thing, school suspends him",
URL: http://www.ajc.com/news/news/boy-does-right-thing-school-suspends-him/nSnwD/ The Atlanta Journal-Constitution. 25 OCT 12.