[WalterBright]

> You are massively overestimating the effect a teacher's input has on student output

Who needs teachers, then, if they are so ineffectual? Might as well replace them with a canned video course.

BTW, every school knows who the good teachers are and who the useless ones are. They get paid exactly the same. Do you think that's a good system?

> There are teachers who are better than other teachers, but it's not generally measurable in "student outcomes".

Of course they are.

> Just like there are better programmers than other programmers, but it's not measurable in "company revenue".

Company revenue is the sum of all the contributions of its workers. A student outcome is not the sum of the other student's outcomes, and is measurable independently.

> Teachers will be incentivized to move to schools or districts with better students.

Sure. And there are only so many of those positions available.

[ryandrake]

My parents and step-parents are all retired teachers so I've seen the system from both the student and teacher's sides (and now also as a parent). School is not like a factory where raw material (students) come in, teachers apply work onto the raw material, and then finished product (educated students) come out. You can measure the students, but you are not measuring teaching quality. Student success is probably close to 95% parents/culture/homelife/nutrition and 5% some result of teacher input. If you have a reliable way to isolate and measure that 5% independently, by all means, suggest it to your local school board. They would absolutely love it.

[aleph_minus_one]

> Who needs teachers, then, if they are so ineffectual? Might as well replace them with a canned video course.

Replacing teachers by canned video courses does not a priori sound like a bad idea.

The central reason why this is not done is that school also serves as daycare, so you need some employees to supervise the children, i.e. removing the teachers will hardly decrease the employee count. All together, if we consider the additinal cost of creating the video courses, this measure would hardly decrease the cost of schooling. So politicians think "never change a running system" and "avoid the trouble with the teacher's unions" and leave everything as it is.