Violence is far less common at schools than in the general population, and considering what I am going to say next, it impresses me that violence isn't even more common.
Lots of kids don't want to be at school. While physical aggression is not as common, it is still elevated for a lot of students, and there is a substantial level of verbal aggression. School is compulsory. Teachers are asked to serve as disciplinarians and educators, and students who resent teachers for the former will compromise what the teacher can do as the latter. The disciplinary aspect is compounded by the fact there are lots of rules, some of which are geared for security but have consequences that breed contempt (often quite understandably) for the system. In some cases, there are not enough of the right rules. Cartoons and other programming reinforce the concept that schoolwork is boring and math is hard and that bullies and cliques are a natural part of school -- what is ostensibly an effort toward authenticity is still typically an exaggeration and can perpetuate these problems through a self-fulfilling prophecy. And the more "mature" content on TV tends to be especially violent. Teachers may be role-models for some adults, but they are not role-models for many kids. Standardized testing has uses, but it is much for useful for limited diagnostic purposes than determining who passes/graduates and who gets promoted/fired -- pressuring teachers to "teach to the test" is a disservice for both teachers and students. Having a politicized school board (as we famously do in Texas) makes for some interesting problems, too. There are also battles over curriculum -- it is not easy to create consensus over what is required, what should students have discretion to take, and what should not be taught or does not need to be taught. Parenting and early socialization are quite important. Various school activities are useful, but some of them are time sinks (the DARE campaigns come to mind). There are many other problems: class sizes, do students spend too little/much time per day in mandatory school activities, do students need to spend fewer/more days at school, do students need to space out their school year more, are classes too intense or not intense enough, insufficient counseling services... but I digress. With all of these issues and dysfunctions, we are lucky kids do not act out more often.
As for "liberal agenda," there is just as much as a "conservative agenda." Mandatory pep rallies for football and pretty much nothing else? "Conservative agenda." Using football pep-related activities towards PE credits but generally not extending comparable options to other sports? "Conservative agenda." Moment of silence? "Conservative agenda." Arranging for kids to say The Pledge of Allegiance, and injecting that pledge with "God?" "Conservative agenda."
Regarding school-recognized awareness days, yes, these are quite problematic, because it gives the idea that there is a "Token" period for recognizing the respective groups of people, that their significance can't otherwise stand on its own. The contributions and significance of everyone in society has to be dealt with more matter-of-factly, that it is a matter of *fact* that people from various groups have been contributing members of society and that they are functional human beings. Facts and research can point to these ideas. Integrate this information into existing coursework.
Still, even outside of these facts, it may still be necessary to enforce basic Kindergarten rules to protect kids (without mentioning any discriminatory factors by name). Keep those in force at higher grades, too -- even if they sound a bit plain and simple. If they are simple and elegant enough, those rules won't just protect kids from intimidation and bullying, but they can serve as effective teachers, too (students can look at analogous situation to draw new conclusions).
