The "Hidden Curriculum"

My mother has a Ph.D in the sociology of education and for as long as I've been alive, taught teachers how to be teachers. She currently teaches (among others) a course at the University of Rochester called Race, Class, Gender and Disability in American Education. The course is designed basically to open student's eyes to the problems in education; the biases they have and need to overcome in order to be better teachers.  I've been to many of her classes (she's taught it for a while now) and I've seen and heard many of the racism, sexism and other biases that her students carry into the classroom. Hidden curriculum is basically what students learn in school that isn't part of the curriculum. How kids learn to interact with each other, how girls and boys learn how they're "supposed" to act and how society expects them to act with each other and with the world. My mother's library is right next to my room and it's filled with books all about this and about education in general.
There's a lot of good things about this, but there are also bad sides-the main thing being that every time a teacher says something that is (whether blatantly or not) disrespectful, degrading or just rude to a certain group of people, I definitely notice.
This happened a lot in a certain class yesterday. I'm not going to name the class or the teacher (although most of you will figure it out on your own), just out of courtesy. We were discussing immigration and the teacher was talking about the benefits and problems that comes with people moving in and out of different countries. He was discussing the problems with it, and then said something along the lines of this, "Immigration does bring a lot of problems; drugs, guns, they all come from these people moving into the country." I suppose that some drugs and some guns do come from other countries, but the Europeans, who came to America before anyone else; they brought the guns. There are so many different types of drugs that I think it's impossible for immigrants to have brought them all over. Even the day before, when the teacher was explaining the "push-pull" factors of immigration, he was using a picture of a truck in the mud. He asked how someone would get the truck out of the mud and someone said "Hire Mexicans to push it!" He burst out laughing and even after he recovered, simply said "I don't think there were any Mexicans around."
Sure, it was a little amusing, but he is a teacher. His job is to create a safe, healthy environment for kids to learn in, and if someone goes to class and not only hears a stereotype or degrading comment about their ethnicity or their background, but hears that it is enforced by the teacher, it just engrains the idea that it must be right into themselves more and more.
When we get packets and articles to read, the majority of them refer to a collective group of people as "him" and "he" opposed to "them" and "they."
People spend thousands of dollars trying to fix the education system; fixing students grades and behavioral problems and their self esteem and confidence in themselves and their education. But someone, please explain how these students, whether they come from a privileged or impoverished homes, who already deal with almost crippling self esteem issues are supposed to thrive and learn in an environment where the stereotypes they try so hard to get rid of are reinforced in their daily life?