What you're proposing is not "obvious" to anyone who actually studies education.
>Quite the opposite. The bonus is per student.
How familiar are you with education? Children develop at different paces but are grouped by age, at least until high school. Teachers don't just teach to get the kids to the next grade, or at least they shouldn't. Under what you are proposing, it doesn't make sense for a teacher to spend any time on a kid who is already going to go on to the next grade. There is no incentive to challenge them with harder books, or harder math problems.
Like, we literally already tried this with NCLB. The ended in the most obvious way possible. Teachers taught to get test results, standards were lowered to make it easier to move to the next grade, children who were excelling were ignored by their teachers who had to focus on children who were lagging.
The whole concept behind 'pay for results' is that you think teachers are not putting the effort they could in.
>NCLB was nothing like I proposed.
I encourage you to do some reading on this topic. You're literally just describing a positive incentive based NCLB. You have the same operating theory that the designers of NCLB had.
>It's also not about working harder. It's about results.
This is a meaningless statement.