You will have to increase the educational system's budget. You will have to raise taxes. You will have to build more classrooms. You will have to hire more teachers. You will even have to feed the damned kids, and improve their home life.
There is no "method" that avoids having to do these things. These are the problems you have to solve to reach the intended goal. How you go about solving these problems does not matter.
Use whatever method you want. Sweet talk them. Bribe them. Hire a guy named Vito with a baseball bat. The method doesn't matter. Just solve the problems.
A manager that just says "teachers will be evaluated based on their students' standardized test scores" will get nothing useful, because they did not provide a method, and the teachers aren't empowered to solve their problems in a productive way.
There is no method for a teacher to solve those problems. It's a systemic issue.
What ends up happening is that people will cheat the system so they can hit the target you enforced, while sacrificing some other critical thing you forgot to enforce. In the educational system, for example, what happens is "teach to the test," which causes improved standardized test scores at the expense of actually learning things. And, of course, you get schools that outright cheat when scoring the tests: https://www.washingtonpost.com/news/answer-sheet/wp/2015/04/...
Re: ETAs, those are predictions, not goals. Predictions are good. Most of the article is about the difference between the two.