a fair number of my friends are teachers, so I've heard a ton of their stories.
First off, as a shortcutted teacher (didn't get a true Education degree), you're at risk. Texas has similar programs for bringing in more teachers. The core complaint (as somebody else sort of mentioned), is that these teachers haven't had the full training of classroom management. The result is, these people are less likely to have the skills to maintain order in the classroom.
For those not aware, teachers generally go back to school at least a week before classes start to prep the room and do in-services and such. So normally, he ought to have been used to the classroom before classes start.
Lesson Plans. Yours is the second time I've heard about new teachers having to struggle for lesson plans. No offense to teachers creativity, but in every other job, the new guy is handed directives, not left to figure out what he's supposed to do. In short, any school that hires a brand new teacher without handing them a basic lesson plan, with maybe some room for customization is a school that lacks in management.
Culture shock. Teaching college kids is not the same as teaching a required course to high school difference. It's economics. The college kids PAID to be there, and thus are more motivated to succeed. Whereas, in high school, especially a required course, if there's any problem kids, they are not unmotivated to cause trouble.
Racism. Teachers slowly develop racist mentalities by being exposed to problem schools where the problem group can be easily labeled by race. Here in Houston, while my friend was interviewing, the schools would literally discuss themselves in terms of % of white. As in a higher percentage was a better school. And in practical terms, it was a useful metric. While none of these people are going to join the KKK, they develop a mindset that associates their classroom challenges to a racial profile.
The real reason is that it's about apartment complexes serviing schools. These pack in more kids in a school district which floods schools, going over the standard 25 student per teacher ratio. The apartment complexes are filled with poor people. The poor people tend to be black or hispanic. The poor people's predominant culture is one where school is not valued. These are the kids who cause most of the problems. Which then gets summarized by race.
As for the poor people not valuing education, at one point, my wife had to call the parent of a 9th grader who was failing algebra, the parent said, "so, that's not a big deal." In other cases, the parents would pretend not to speak english, until a spannish speaking secretary was put on.
Conversely, for every school labeled as a failing school, I would bet you money, there are nerds in that school getting A's who are earning them. Which demonstrates it is possible for poor people to value education and succeed.
The problem, as the LA Times is reinforcing by publishing the names and rankings of teachers improvement of kids grades, is that the trend is to blame teachers for bad grades. When in reality, it is more than likely the fault of the students and the parents.
The teachers I know that work in the poorer schools spend most of their time policing than teaching. The bad kids are draining education time from the good kids.
These are the challenges you're going to face in your new job.
Good luck.