As a precautionary system, many schools across the nation have been searching lockers to eliminate the school of weapons and drugs that the students had. The schools had probable cause, meaning that they did have some piece of evidence that says that particular person had illegal objects. This caused an outrage with students and parents alike, saying that this was an invasion of the student's privacy. This case was taken to the supreme court, who ruled that the schools did have the right to search.
At my school, there's a lot of drugs and the locker searches are few and far in between. But somewhere it says that they're able to search lockers, but mostly the middle schoolers use their lockers because all of their classes are in the same hallway. On the highschool side, some people have classes in all four different hallways. So using lockers can be impractical and time-consuming, so just about everyone carries around their backppacks to their classes. Bad for the back, but you're not late and have time to chat or even go to the bathroom between classes.
Every so often, we have a drug dog come to our school, they don't serch the locker unless the dog barks or something. One kid got in trouble for having fake weed.(Idiot.) Don't know have they found it since it was just leafs crumbled up.