If the Washington Education Association gets its way, we’ll be voting to approve another initiative to reduce class sizes this November. It’s a mistake we’ve made before. It’s one we should not repeat.

In 2000, Initiative 728 passed with more than 70 percent of the vote. The initiative, billed as a class size reduction measure, also provided funding for professional development, early learning and other purposes. Well, it didn’t really provide funding. It redirected money from a fleeting state surplus, one that disappeared shortly after the initiative passed.

Legislators routinely suspended the measure when budgets were tight. In 2012, following the state Supreme Court’s McCleary decision finding that the state was not meeting its obligation to fund basic education fully, they repealed it. Legislators reasoned that eliminating I-728 freed up some state money to help satisfy the court’s order to ramp up school spending by billions of dollars. The repeal was overdue. An earmark without a dedicated funding source is an empty promise, a gimmicky attempt to bypass the budget process by carving out funds without oversight.

Fourteen years later, advocates for the WEA-backed Initiative 1351 show that they learned two important lessons from the I-728 experience: Hide the costs and give the carve-out constitutional protection.

Like I-728, I-1351 doesn’t raise taxes. It imposes costs and leaves it to the Legislature to find the money. The initiative mirrors bills introduced in the Legislature this year. Analysts estimated that, when fully implemented, the measure would cost $3.4 billion a biennium with an even greater unfunded burden laid on local school districts.

Finding that kind of money isn’t easy. Generating the cash for the state share by raising the sales tax, for example, would cause the state rate to climb from 6.5 percent to nearly 8 percent. For proponents’ campaign purposes, it’s important not to talk about that.

The initiative goes well beyond what’s required under McCleary. There’s class size reduction already built into the existing definition of basic education. I-1351 would add more than $2 billion to the funding challenge. Hoping to gain constitutional protection for its staffing requirements, initiative backers specified that the provisions are “to be considered basic education funding … in accordance with the McCleary decision.”

If adopted, the measure would require hiring 12,000 teachers, plus a legion of administrators, librarians, nurses, social workers, psychologists, custodians, “parent involvement coordinators” and, well, you get the idea.

It’s a lot of money, a lot of new positions, and — not incidentally — a lot of new union members. It’s also a lot of statutory rigidity. For a group that rails about the prescriptive nature of standardized testing and rigid accountability standards, the union would happily impose a fiscal straitjacket on local school districts, micromanaging staffing and compensation policies.

The state’s current commitment is to reducing class sizes in early elementary grades, where the research shows smaller classes can have the greatest positive effect. For older students, though, the evidence of educational benefit is mixed.

Matthew Chingos, a Brookings Institution scholar, reviews the research in an article published by the liberal Center for American Progress. He finds that “across-the-board reductions in class size at the state level are likely to yield disappointing results.”

He points to unsatisfactory outcomes in California and Florida, two states that pumped a lot of money into reducing class sizes. One problem may have been that the large-scale policies required schools “to hire so many (inexperienced and potentially less effective) new teachers.”

Of all the current approaches to education reform, class size reduction is the most costly and least cost-effective. The high costs crowd out funding for other measures, including increasing teacher pay. As Chingos points out, “teacher quality is the single most important in-school determinant of how much students learn.” To recruit and retain the most effective teachers, we may need to pay more for them and jettison the lock-step compensation schedules.

The Legislature has spent years on education reform — defining basic education, increasing funding, setting standards and requiring accountability. The work is not yet done. This is the kind of work that will never be done. But we’re beginning to see progress. I-1351 would undercut that progress and take us in the wrong direction.

Richard S. Davis is president of the Washington Research Council. Email rsdavis@simeonpartners.com