A new plan to base some teacher salaries on their performance leaves a crucial question up to each school: how to measure performance.

A Brooklyn school leader, Daniel Rubenstein, has an idea how to figure it out. Look to the private sector.

A longtime teacher, Mr. Rubenstein said he supports the program Mayor Bloomberg is testing in 200 schools this year, which will let teachers participate in allocating thousands of dollars in bonuses if their school shows performance gains.

But he said a host of complications, from the difficulty of measuring who is a good teacher to the problem of inadvertently inviting sly minds to try to “game” the system, make the policy difficult to execute in practice.

So to plan his own school, he is turning to a place where people have been cracking the problem for years: the private sector, where his recent travels range from Goldman Sachs to a Connecticut clothing store that reels in some of the highest sales per square foot in America.

“You have to learn from the best organizations, regardless of where they are,” he said.

The pay plan shaping up is unlike traditional school policies, which mainly reward seniority, but also unlike basic merit-pay ideas elsewhere that offer bonuses purely based on test scores. Mr. Rubenstein said his more complex approach — he wants to reward teachers whose own students do well on tests, but also teachers who show good behaviors that tests do not measure, such as helping their colleagues — comes in part from a Westport, Conn. clothing store, Mitchells, where an owner of the company, Andrew Mitchell, was Mr. Rubenstein’s college roommate.

As Mr. Rubenstein began to learn when Mr. Mitchell helped outfit him and his groomsmen for his recent wedding, Mitchells strays from a traditional scheme of paying strictly by commission. Instead, the store adds other variables to tabulate its employees’ paychecks, such as the rate at which an associate sends his customers birthday cards, the relative loyalty of the crowd at his trunk shows, and the sales figures of his larger team.

The complex formula is meant to encourage not just strong results, but behaviors that lead to strong results, Mr. Mitchell said. “I don’t care about sales at all. I care about building relationships with my customers. If I have great relationships with my customers, sales will happen,” Mr. Mitchell said.

Mr. Rubenstein said he hopes to learn from the tactic. “When you say assess or an assessment, everyone thinks that means a pen-to-paper test. And that’s the fallacy: That everything comes down to a few very rigid measures. It doesn’t,” he said. “Look at what Mitch is doing. They’re measuring birthday card sales!” A like-minded school pay plan, he said, would build in incentives for teachers to take other steps to help their students, such as sharing their lesson plans with other teachers or taking on a leadership role in curriculum planning.

Other aspects of Mr. Rubenstein’s approach to judging his employees come from Goldman Sachs, a company whose work ethic he said astounded him on several recent visits. He said he plans to mimic the company’s so-called “360-degree” evaluations, in which managers review subordinates — and the subordinates review them back, a process he said leaves no one shy about improving.

Mr. Rubenstein said he has not yet visited Google’s New York City headquarters, but he has studied the company’s business plan. He is thinking of ways to mimic the company’s recruiting schemes, which include holding programming contests, advertised on billboards and Web sites, whose prize is a company job.

In addition to companies, Mr. Rubenstein has been studying the recommendations of a group of teachers at the Center for Teaching Quality. He said he admires an idea in a paper they put out recently on performance pay, which argues for setting base salaries according to competence rather than seniority.

The report suggests three competence levels: novice, professional, and expert.

A final pay plan for the school is still being drawn up, and it won’t be final until the school’s own review, from a state authorizer of charter schools. The authorizer denied Mr. Rubenstein’s first application this year.