One thing is for sure about a plan to change how Minnesota teachers are evaluated: Even if it becomes law, it won’t work. At least not the way its supporters hope it will.

There’s a lot of good to be said for the basic idea that’s working its way through the legislative process: Reward good teachers for their skill, weed out the weak ones regardless of their seniority.

Who wouldn’t want their children taught by the best? Who wouldn’t want to work alongside colleagues who are all innovative and hard working?

There are, however, many pitfalls between idea and execution, particularly in this case.

Perhaps no problem is knottier than that of designing incentives and assessments that will produce desired results. Business has grappled with the problem for centuries: How do you create a pay and review plan that will reward the best workers, get rid of the bad ones, avoid accidentally classing good workers among the bad, not run up costs, and still provide the kind of opportunity that attracts the best and the brightest?

The first problem lies in defining goals. Unless we can agree exactly what outcome we want teachers to produce, it is not possible to assess or reward results accurately.

The second problem lies in how we measure results, and this is one of the big arguments about the plan that lawmakers approved earlier this week. Student achievement on standard tests might sound like a good yardstick. But what happens to the teacher who, through the luck of the draw, gets a below-average class full of students a couple of years in a row? When the results are bad do we run that usually good teacher off?

Or what about the usually excellent teacher who hits a rough patch in her personal life — bad health, family problems — which is reflected in her work. Happens in every profession. Should we run off a quality professional because of a short-term problem?

On the other hand, what’s to keep a teacher from “teaching to the test,” producing students who excel at passing a specific exam, but whose knowledge is only skin deep? When money and jobs are on the line, people find the easiest way.

And as was proven in a Chicago schools study, those who are desperate will evade the rules.

So much for basing evaluations on student achievement. What about peer reviews? Shouldn’t teachers be able to evaluate each other’s work? Sure. But peer review is infamously flawed, because very, very few people have the nerve to produce a bad review when it might cost their subject — even a complete stranger — money or a job.

Then there is the biggest problem of them all: The whole system of evaluation and reward is being planned by people who are very popular, but basically clueless on the subjects of education and economic incentives — in a word, politicians.

To make matters worse, the politicians have to make a plan that sounds good — which is not the same as being good — not only to their own colleagues but to a governor whose views are radically different. In another word — a compromise.

So added to the fiendishly difficult challenge of matching rewards to goals — something brilliant business executives can seldom get right — is the reality that Minnesota’s plan will be hashed out by committees.

Then, when flaws in the plan become apparent, the only remedy will be to go through the whole political process again with the same slim chance of getting it right.

Those are not encouraging words for those who want to see improvements in education, including the educators who will be the victims — er, make that “subjects” — of the new rules.

There is no perfect way to work through this process. But if legislators wanted the best possible results, they would appoint an educator, an economist and a politician — three smart, distinguished people — to a panel with authority to establish a review and incentive plan revise it annually for the next five years.

There would be some rough patches along the way, because changing a decades-old system is never easy. But we might eventually end up with something that everyone could live with — including better-educated kids.