The problem isn't that there are police officers in schools.
The problem is that police officers are no longer the servants and protectors they used to be, but are now violent and egotistical thugs.
If our police were reasonable, rational, brave, principled protectors of the innocent and agents of Justice, their presence in schools would be a boon. They'd be remarkable role models for students, and they'd help impart values of generosity, self sacrifice, community, honesty, integrity, fairness, bravery, toughness and gentleness alike, and countless other positive values that would be immediately evident in their behavior and comportment.
As it is, they're ignorant, impatient, self-centered, power hungry bullies who use force and intimidation to maintain a status quo. They have no interest in fairness or Justice, no stake in defending the weak or giving voice to the voiceless. They exist purely to enforce the arbitrary rules established by whichever cruel or idiotic figurehead controls their paycheck. They will not go out of their way to help people in need, they will not put themselves in harm's way for the sake of others, they will not speak out to support an underdog or a minority. They are hired goons wearing the mask of respectable authority.