A teacher is a human being, and as a human being I want to learn from and teach those who are willing to learn from and teach me. Some students either can't or won't learn, and it's my job as a teacher to discern the important difference.
Middle schoolers are further along on life's journey than elementary school students and thus easier to decipher the direction their lives are taking and which forks in the road they have chosen.
Some students have yielded to the rot in their lives, have chosen unwisely, and have been beguiled to give up their dreams for a better world. They have chosen to climb aboard a broken down cart of educational mediocrity.
I strive to have no conceit towards those riding in wobbly wagons and no contempt for those with hobbled hopes.