Be fair.
When you have a classroom of 40 hormonally driven teenagers, you need to have order to do your job.
I have constantly been amazed at the ability of kindergarten teachers to keep up with a classroom of 25 five year olds. I have trouble with just one!
Most of the public school teachers we've had (with one or two exceptions) have been excellent, very professional and dedicated.
The problem that I've seen after volunteering in the classroom is the inexorable pace of school (which is paced to the average student, slower and more advanced students are cheated under this structure).
And so you spend a whole lot of your time establishing order.
And the ones who are already orderly during this time are learning what?
That order is the most important thing. Shut up and sit down. Don't ask any more questions; we have to move on to the nervous system.