It is true that many teachers react very badly to the best students, particularly where the students are very evidently smarter than the teachers. In this age of ready access to information, any student with a drive to learn can quickly be head-and-shoulders above the average highschool teacher in a given subject. Good teachers help such students. Bad ones get jealous and seek to harm them.
What you say is true, but I've seen this happening even with good teachers. I think there's a few reasons for this - first, if you have a large class and a student is already meeting all the standards, you're going to spend the time you have on the students falling behind. Teachers are going to want all the students to know what they're supposed to for that grade, rather than to have some advanced far off the grade while others fail.
Even if they had the time, there seems to be very little interest in advanced students across the board, and few if any programs put in place to meet their needs.
Secondly, there aren't many opportunities for students to demonstrate that they exceed the standards. Getting a class test entirely correct demonstrates that they know what is being taught, but nothing more. One thing I like about the standardized tests they're given now is that the computer will adjust and ask more advanced problems if the students get answers correct.
When I applied to secondary school, I barely made the cut and was one of the lowest-scoring students to be accepted that year, only ranking around the 4th percentile of those accepted. Once I started attending, I performed exceptionally well, ranking around the 95th percentile, give or take 5. It was mainly due to the fact that a large minority of my primary school teachers had biased opinions about me and our personal differences affected my grades.
